The AM Forum

Hi Elmers,
I recently bought a Harvey Wells Bandmaster TBS-50C and I want to use a Heathkit HP-23 ps to power it. I am somewhat a newcomer to restorations so I need fairly detailed instructions. I have had some success at rebuilding tube receivers over the past few years but I have never tackled a transmitter. My goal is to set up s "50's" station using the Bandmaster and my R390a. Any help would be greatly appreciated.
Regards,
Tom N0TJL

Tom,

Are you willing to dedicate the HP-23 to the TBS-50 rather than using it to also power other rigs in its stock configuration?  If so I would rewire the HP-23 HV supply from a voltage doubler to a full wave bridge and use this section to power the TBS-50.  Set up as a normal full wave rectifier I would expect around 350-375 volts under load with reasonable size filter caps.

The LV supply of the HP-23 is a little marginal to power the TBS-50C, the LV transformer secondary and filter choke might stand up to the current OK but the TBS-50C is well over the normal rating for the HP-23 series LV supply and the voltage is going to sag considerably.

Thanks WQ9E,
I'm not sure exactly how to do this. Is there detailed info on this process somewhere that I can access.
Regards,
N0Tjl

this is what separates the men from the boyz .... get a schismatic of the hp23 and get one of the ham radio handbooks and get into the section on power supplies ... start comparing and list yer questions .... you can do this !

Hello W4BFS,
I have the HP-23 schematic and the Bandmaster ps schematic. Would this be a good place to start?
Thanks,
Tom, N0TJL

yes .... start comparing .... Rodger is spot-on about use of the hp23 .... what needs to be done first is to determine what voltages are used for receiving and then for transmitting .... a lot of rigs from that era switched on power amp stage b+ during transmit .... see what is going on in the HW ps .... this will jump start the process

the longest journey begins with a single step and ends with the same

Great, I'll get on with it.
Thanks,
N0TJL

Tom,

The ARRL handbooks from the mid-60s through mid-70s will have a theoretical explanation of various rectifier configurations (half wave, full wave, full wave bridge, etc).  along with practical circuits using them and the same is true of the Orr "west coast" handbooks of the same era.  I prefer Orr's writing/editing but either from the era are good.  Some of the earlier ARRL and Orr books are available as free PDF files on the web but I am not sure if any of the later ones are available.  A large library might have them available or you can find them on ebay or at hamfests.  A few of these are a very worthwhile addition to your technical library and you will use them frequently in the future.

If the HP-23 filter capacitors are original you will want to replace them during the modification.  With the HV winding reconfigured to a full wave bridge, 450V rated will work fine.

Since the TBS-50 was originally often used as a mobile rig, for an authentic station you could add one of the mobile receivers (Multi-Elmac PMR series, Heathkit MR-1, one of the Morrows, etc.).  You will find that for most of these receivers the low voltage supply of the HP-23 will be about right so you slightly modified HP-23 is the basis for a versatile setup for many pieces of vintage gear.

http://www.heathkit.nu/heathkit_nu_HP-23B.html

It seems the HP-23 came in more than one flavor.

RSWL

The basic design was pretty stable over the years.  A switch was added so that the LV level could be chosen (and the supply could be turned off via that switch) so that rewiring wasn't needed to select voltage and the next version removed the variable bias feature from the supply since Heathkit provided the bias pot in the gear.  This made it easier to share the supply between multiple pieces of gear, having the bias pot in the supply instead was preferable when a single rig was switched back and forth from mobile to fixed station use.

The HP-23 series supplies are well designed and reliable as long as they are maintained (basically replacing filter caps as needed).  A version of this supply was built into the SB-400/401 transmitters.

Some of the most versatile external supplies were the Swan series and these are great supplies that can be used with a lot of rigs.  I also picked up 5 older Galaxy supplies at a hamfest several years ago and I have used these with several homebrew and commercial rigs.  I will be rebuilding something soon to go with a Trio TS-510 transceiver I acquired without its power supply.  The TS-510, also sold as the Allied A-2517, has a somewhat unusual external power supply which contains a fairly high current 150 volt regulator using a 6BM8 with a neon bulb reference source.

I do intend to recap the HP23 asap.
Regards,
N0TJL

Drake also made a nice supply, same basic setup as the Heathkit one.
I picked a nice homebrew copy of a Drake supply with a very nice large Hammond transformer in it for $15.00 on ebay.

I agree about the Drake supply and that was a great deal on the homebrew copy!  Drake supplies usually sell at a premium price, probably because not as many Drake T-4 and TR-3,4 series are getting parted out as some of the other brands so there isn't a supply surplus.  I used a Drake supply for quite awhile to run my Gonset G-76, the only major change was the addition of a relay and snubber network for switching the HV output off for receive as is done with the real Gonset supply.  A few years ago I found the proper Gonset supply and the Drake supply was re-tasked to power a TR-6 with TC-2 setup.

Hi W4BFS,
HW requires 300 or 400V 275ma and 6V or 12V for the filaments.
HP23 delivers HV of 700V 250ma and LV of 300V 150ma and 6.3V or 12.6V for the filaments. The went on to say that on the LV high tap the duty cycle is continuous up to 175ma. What do you think?
Thanks,
N0TJL

Tom,

Keep in mind that if you reconfigure the HV doubler to a full wave circuit you can safely draw about double the current it is rated for in its current configuration.  That winding is much better suited to the demands of a TBS-50C running in AM mode.

The LV supply, even on the high tap, is going to be well under 300 volts under a 275 mil load which greatly exceeds its design parameters.  It would be OK for a TBS-50 running only CW but not for operation on AM.

Please keep in mind that the TBS-50 has exposed HV on the back so be careful and if your household has small children or pets it would be a good idea to at least use electrical tape over the exposed terminal strips.

Hi Roger,
This old HW can't have been operated for a long time. It took a bit of penetrating oil to free the bandswitch shafts. It might be a good idea to bring it back to life on CW first then move on to AM. To accomplish this, can I just wire an 8 conductor female connector on the xmtr end of the HP23 power cable and insulate off the unused conductors? I thought I would attach a plexiglas rectangle over the exposed contacts on the back panel of the HW.
Thanks,
Tom N0TJL

Tom,

For getting it going on CW that should be fine.  Set the switch on the back for 350 volt output and leave the bias and HV leads from the HP-23A disconnected.

Even with crystal control I wouldn't be surprised if there is some chirp when keying the TBS-50 on CW because the HP-23 as configured will have a significant change in output when keyed.  It may be OK on crystal and would be fine if driven by an external VFO with its own power supply.  Once the HP-23A supply is reconfigured to use a heavily filtered and lightly bled HV supply then the voltage regulation should not be an issue.

Good luck!

Rodger,
That sounds good. If I can't get it going on CW, it will never work on AM. I intend to use crystal control and am surprised that the proper crystals are so hard to find. I bought some crystals that were fairly close to frequency and ground them into the amateur bands. I used the signal generator - frequency counter - oscilloscope hookup to check grinding progress. This system works great. I am looking for an original HW VFO, I hear they are rare and expensive.
I appreciate the help.
Thanks,
Tom  N0TJL

Hey Tom
On the VFO the VF-1 is a good choice and not real expensive. Ive found that the H-W VFO drifts pretty badly. Have had three of them. Useable on 80mtrs 40 you have to retune about every 10 secs forget the higher bands.
P/s output need to be 475vdc or less. If you run more bad things will start to happen. Tank components will flash over and sometimes the modulator tube sockets will arc too.
GL Great and fun transmitters
Terry N3GTE
http://www.swedeart.com/harvey/html/n3gte.html

Rodger,

Your TBS is a really nice looking, and I suspect earlier example, because of the much better looking name plate.  

Mine went under the "knife" at what appear to be several times in the past and was pretty messy inside.   Although its a "C" I got it with the mic preamp chassis, which hadn't been installed.

(http://i670.photobucket.com/albums/vv62/mikeinkcmo/Radios/Harvey%20wells/Harvey%201_zpsrcr1a4dh.jpg) (http://s670.photobucket.com/user/mikeinkcmo/library/Radios/Harvey%20wells?sort=3&page=1)

Mike,

That is a nice TBS-50 you have also!  There are a lot of ragged looking ones out there and I bet a lot of them were run in mobile service and have the battle scars to prove it :)

If they had continued making these transmitters with a simple power supply kit I bet they could have sold a few to the growing novice classes of the later 50s.  The basic style, particularly with the VFO base, with a new color scheme and knobs would have looked right at home in the late 50s and early 60s.

Thanks everyone for the help. I have another question, what is the connector on the top of the TBS-50 used for? I have seen these transmitters in use and have never seen anything connected there.
Regards,
Tom

If you're talking about the RCA Phono plug mounted on the pair of 2" spacers just behind the short tuning capacitor, its the 2 meter antenna connector.
(http://i670.photobucket.com/albums/vv62/mikeinkcmo/Radios/Harvey%20wells/Harvey%205_zpsf901tq72.jpg)

(http://i670.photobucket.com/albums/vv62/mikeinkcmo/Radios/Harvey%20wells/Harvey%20B_zpslmu1vmzo.jpg)

I overlooked the two meter section of the manual so I missed that part. Thanks for the info.
Regards,
Tom N0TJL

Harvey Wells was several decades ahead of the modern Yaesu and Kenwood "DC to daylight" rigs :) 

Although the power is very limited on 2 and efficiency is poor forcing the input to be strictly limited it was a pretty big accomplishment to sell a rig that cover 80 through 2 meters and could be modified to operate on 160.
 

Tom,

Your unit looks pretty clean--good luck with your restoration.
There were several articles I found useful on my restoration of a TBS-50C:

http://ab7yd.home.comcast.net/~ab7yd/TBS50D.htm  and

http://www.swedeart.com/harvey/articles/tbs50/cq1955-hw1.jpg

The latter article describes adding a 12AU7 speech amplifier between the carbon mike and the 6L6 modulators, and was necessary for me to easily achieve 100% modulation using a T17 microphone.

We powered the rig with the stock APS-50 power supply, and we currently achieve 20 watts carrier on AM.

73
Eugene/AF9O

Here is the original H-W 50D schematic, for use of D-104s and the like. (http://i670.photobucket.com/albums/vv62/mikeinkcmo/Radios/Harvey%20wells/Modulator%201_zpsgouojrjq.jpg)

Terry,
As a licensed amateur, I am almost embarrassed to ask the following questions. Here goes. On the HP23 power cable, is the filament common (white wire) connection the same as ground? One side of the filaments on the HW goes to ground. There is a separate ground connection (black wire) in the HP23 cable. Can I leave this disconnected in the HW socket end of the cable? Is the HP23A the same as the HP23B? I have an HP23B power supply and an HP23A manual. I never really looked at the labels surrounding the output connection on the HP23 case. Upon checking this I find that they don't seem to agree with the way the HP23 manual instructed me to wire the socket on the new cable that I obtained - confusing. Maybe I am overcomplicating this but I would rather not become a crispy critter.
Thanks in advance for your help.
Tom N0TJL 

Ground filament common to TBS-50. Depending on how you have the heaters wire on the TBS-50 pick either 6 or 12v from the HP-23.
Terry N3GTE

Hi Terry,
Thanks for the info. I answered my own question on the HP23 supplies. I found an article that compares the Heath supplies. The HP23-B that I am trying to use supplies only 12 volts. The 6 volt connection was dropped in the B supply. My manual is for the A supply, thus the confusion. How do I connect the terminal strips on the HW for the 12V? I connected up the HP23 and the HW, switched the HP to 300v turned on the power switch on the HW and measured 364v on the plate of the 807. Of course the filaments did not light but it looks like progress. now I just need to get 12v to the filaments.
Tom N0TJL

Jumper  terminals 3and 4 together on the terminal strip 1and2 should have no connection on the back. Apply 12v to pin 2 of the octal plug and ground.
Never measure B+ at the plate of the final tube. Always measure at the cold end of the tank coil or if it has a plate choke at the cold end of it. At the plate there's a bunch of RF that will make your meter not read properly and could damage it. It's like give your meter a hotfoot.
You have 364vdc without a load on it. Let's see what you with full RF output and modulation.
Terry N3GTE

On the 50C schematic is the tank coil L15 and is the cold side toward sw4?
Regards,
Tom N0TJL

Let's go with terminal 5 on the back panel. L-15 is the 2mtr tank coil.
Terry

I will check it at that terminal. Rewired socket and terminal strip per your instructions. The filaments lit up so I tuned it up into my Yaesu 150 dummy load watt meter and got 11 watts out. Plate read 95 mw and grid read 1.8 mw. No smoke, no sparks. Looks like progress. How do you tune your HW? I could use a step by step. The HW TBS-50 manual is a little vague.
I have a Sonar CFC vfo/exciter. It puts out 6 watts on 80M and a little over 4 watts on 40M. Would this work as a vfo for the Bandmaster? Could it be connected directly to the crystal socket on the front of the HW? It has its' own power supply.
Thanks again,
Tom N0TJL

Milli ampers, not milli watts?
 

Of course it is ma not mw, don't know what I was thinking about.
Tom N0TJL

Could anyone tell me if a Sonar CFC Exciter/VFO could be used with the HW Bandmaster 50C. I obtained a CFC and it puts out about 4w on 40M and 6W on 80M? Could it be connected to the crystal socket on the HW? The CFC has its' own power supply. I don't know much about the HW VFO.
Regards,
Tom N0TJL

Tune up is the same as any tube tx. You need abt 2ma of grid drive. Adj PLATE knob for MIN current. Adj LOAD knob for max output. Redip the the PLATE and adj the LOAD for max again.
The TBS-50's load cap is too small to load it properly on 40 and 80mtrs. So as per the manual you need to add a cap from the ant post to ground. I think it's 50pf for 40 and 100pf 80mtrs check the manual for values. This could be why you are only getting 11w out. That about what you would get w/300v for the HV.
That VFO seems to be a little to robust for the H-W. I would build an attenuator to knock the output down to abt a watt or so.

I am not familiar with the CFC so since its an exciter, what is its output load impedance ?  50 /70 Ohms or higher ? load it with resistor(s) and capacitivlly couple the output to the oscillator starting with small cap (say 10pf or so) ... go up with cap value to provide equivalent drive to crystal .... if other values change (drive, grid and plate currents) the the xtal oscillator could be moding so tune it up with a xtal first and note readings

The HW manual does mention use of a small variable capacitor across the antenna terminals on 80 and 40. At present, I intend to use it on 20 and above so I should be ok until I put up a 40M antenna. Your tune up procedure is very similar to the way I tuned it up so I guess I'm ok there. Do you have any suggestions for building an attenuator? What would happen if I didn't use an attenuator? The output impedance of the CFC is listed as between 75 and 300ohms.
Thanks guys,
Tom N0TJL

this is an experiment with getting the xtal osc to just act as a buffer so that is why I made the statement about moding ... if the osc/vfo switch is placed in the vfo position then a tendency to mode will be greatly reduced and you just need a few volts of rf to drive the 6aq5 as a buffer

I would use a string of say (qty 7) 10 Ohm 1W or so carbon comp resistors in series as a load for the exciter ...keep the leads short ... at 6W out each resistor should develop about 9Vpp of rf across them ... start with the resistor closest to ground with the 10 pf coupling cap to the Hw vfo input ... see if you get drive ...experiment and have fun

How would this look schematically between the output of the CFC and the crystal socket of the HW?
Thanks,
Tom N0TJL

I don't have a schematic capture pgm so roughly ....

     cfc hot ---------- res ---- res ---- res --- res --- res --|-------- cap ------ HW vfo hot   
                                                                                 |
                                                                               res
                                                                                |
                                                                                |
                                                                               res
                                                                                |
                                                                                |
                                                                               gnd

this should provide up to 18Vpp  to vfo input depending on capacitor value .... you can move to different res junctions for differing drive reqmts






 

How about using standard T or L pad circuits?

Simple to build.  Calculators are available by the dozens on the web.  Get the precise level of attenuation you need.

http://chemandy.com/calculators/matching-t-attenuator-calculator.htm

https://troester.org/ls/lpad.html

Or a Pi Pad
http://www.random-science-tools.com/electronics/PI_attenuator.html

Thanks guys. I'm not sure of the amount of power needed to feed the HW and thus the level of attenuation I need. I'm curious, what might happen if I fed the 6w output from the CFC through 300ohm twin lead directly into the HW with the HW Crystal/VFO switch set to VFO.
Tom N0TJL 

probably fry the 6aq5 grid

That attenuator is looking better and better.
Regards,
Tom N0TJL

Would it be possible for me to breadboard the attenuator until I get the final configuration worked out?
Thanks,
Tom N0TJL

I would think so since you are looking at 80 and 40 mtrs ... there should be a good combination to be worked out by experiment that will work on both bands .... the 47k Ohm 6aq5 grid resistor will help level things out .... this will be most satisfying to work out ... 73

The carbon resistors are on order and I will get on it asap. Sounds like fun.
Thanks,
Tom  N0TJL

Is there any flexibility in the value of the capacitor?
Thanks,
Tom N0TJL

yes ... calculate the value of cap reactance :   Xc = 1 / (2 x pi x freq x c ) so for 10pF at 7 mHz this equals about 2.2 kOhm and this will double to 4.4 KOhm on 80 mtrs ... this sets up a desirable condition for 80 or 40 mtr op as this tends compensate for the increased output on 80 mtrs of the CFC exciter

the 6aq5 has around 13V of bias generated by the cathode ckt which is class a operation and is ready to amplify (or oscillate with the inductor in the ckt) ... as you drive it as a buffer ... swings larger than this will swing the grid into grid current which will cause grid rectification and gen negative grid bias so the circuit tends to be somewhat self regulating, at least to a point ... the output spectrum will be richer in harmonics with overdrive and could possibly tune up on one of those .... by the way the HW manual suggests 80 mtr crystals for both 80 and 40 mtr operation .... both will probably work but again could have trashy output

Can I get away with two 18pf capacitors in series? Using the formula for capacitors in series I get 9pf. Is that close enough? The CFC is only a two band exciter (80 & 40) and I intend to work 20M initially. So I will tune up with the HW set to 20M and the switch set to VFO. I shouldn't exceed 2ma grid drive. Is that correct?
Thanks,
Tom N0TJL

sounds like a plan to me .... the series caps should be fb .... nothing seems to be critical with the 47k biasing resistor ... check the note at bottom of schismatic for vfo freq / band .... grid current staying close sounds like happy happy happy to me

In adjusting the attenuator, do I remove resistors on the ground leg or the hot leg?
Thanks a lot for all of the info and patience.
Regards,
Tom N0TJL

don't remove resistors, just move the tap point ...start at the first junction between the grounded resistor and the next one in line

no sweat .... I used to teach electronics for the state of Tennessee in an adult  vocational program

You know your stuff. I worked as a microbiologist for 43 years - not much exposure to electronics other than physics class. Nothing practical there.
Thanks,
Tom N0TJL

Hang around on this Forum for the next 43 years and you'll be an expert ;D

Fred

I'd be 113 years old.
Tom

Just keep the dust off, and the bugs out, you'll be fine. ;D

Does anyone know anything about use of the tuning control on a Barker and Williamson model 381C TR switch? I found a manual for the Model 381 on BAMA but the 381 has only the band switch and no tuning control. I would like to use this unit with my r390a and the HW Bandmaster.
Thanks,
Tom N0TJL

new thread

Hello again guys,
Another HW/Sonar CFC question. I intend to key the CFC and run that output through the attenuator into the crystal socket of the HW with the switch set to VFO. Do I need to short out the key jack on the HW in order to complete the circuit?
Thanks,
Tom N0TJL

looking at HW schizmatic the key line takes both 6aq5 and 807 cathodes to gnd .... with sw6 in phone position all are grounded .... to avoid having the exciter going while in receive, you may need another ptt relay contact to key the CFC

Hello BFL,
At this point in time, I intend to operate cw only. I will need to convert the HP23 ps to full wave from voltage doubler before I can get enough soup to operate AM. To avoid relay work, could I follow the info at the bottom of pg9 of the HW manual where it discusses keying the vfo? Should I add a jumper between pin 8 and pin2 of the terminal strips?
Thanks,
Tom N0TJL

Whoops. Upon closer examination, it looks like I should connect the CFC vfo across pins 2 & 8 on the terminal strips - 8 to hot side and 2 to ground side. A  jumper wouldn't do it. Right?
Regards,
Tom N0TJL

I can't answer this because I don't know how the CFC is keyed (no schiz-o-matic) .... if it is also cathode keyed, possibly ...if something else would have to isolate/buffer somehow

n.b.  just went and looked at HW vfo schismatic ... it is also cathode keyed thru pin 2 ... lotsa drive from a 6ag7

CFC schematic shows hot side of key jack connected to the cathode of the 6L6 tube through a 1500ohm resistor. The tube complement of the CFC is 6SK7 oscillator, 6V6 buffer and 6L6 buffer-doubler.
Regards,
Tom

this has become interesting inasmuch as if the CFC keying line is connected to the HW keying line this would place at least 6 cathodes in common waiting to be grounded for operation .... this might be a new record and makes you wonder what the keying note will sound like

I would probably clip lead test this by measuring the cathode voltage developed by each piece by itself and then connecting them together and remeasuring the combination .... I wouldn't be surprised to see around +40V or so on each and then together .... probably will function but with a strange keying note (guessing) ... if the voltage gets much higher then some heater to cathode voltages limits may be exceeded

Would it help if I emailed the CFC vfo schematic to you?
Regards,
Tom

well, it might avoid an unexpected smoky surprise


n.b. 11 apr 15  .... just reviewed the CFC schizmatic that you emailed, Tom .... the buffer and final are cathode keyed with the vfo osc left free-running ... I think you could bypass the 6l6 by unplugging it and making a connection from the 6l6 grid pin 5 over to the HW thru a short piece of coax ... no antennuator needed .... would need to verfy vfo freq to HW requirements ...

of course the original plan with the attenuator is viable just check the unkeyed key line voltages for compatability (clip lead test)   

I will remove the 6L6, insert the center conductor of the coax into pin 5 connector, ground the shield to the chassis, connect the other end of the center conductor to terminal 8 on the HW connector strip and the other end of the shield to terminal 2 of the HW connector strip, say a short prayer and key the sucker. Would RG-6 75 ohm coax be ok?
Regards,
Tom N0TJL

no, not what is in mind

the 6L6 pin 5 connection goes to the HW vfo input thru a 100 pF or so mica cap and then the short run of coax ... you will need to see which is grounded and which is 'hot' .... this is the buffered rf from the cfc vfo

the CFC key jack connection goes to the HW connector block 8 with gnd to gnd

may have to take another look at this when trying AM

In the 6L6 tube socket, I will plug in my spare octal plug (can't believe I have one of these in my junk box) to which I will have soldered a 100pf silver mica cap to pin 5, other end of cap soldered to the center conductor of a piece of RG-6. The shield of the RG-6 will be connected to the chassis. The other end of this will be connected to the crystal socket (shield to outside jack of crystal socket) of the HW with the switch set to VFO. I will then make a connection from the key jack of the CFC - hot side of the jack to #8 on the HW connector strip and gnd side to #2 on the HW connector strip. Key will be connected to the Key jack of the HW. I will then turn it all on and key the sucker.
What do you think about this?
Regards,
Tom 

I believe its worth a try

Hello W4BFS,
Wired it up per your instruction and powered it up. Grid read 1.2ma, plate read 100ma at resonance and output power read 10w. Had the CFC set at 3525kc, the HW set to 20meters and picked the signal up at 14100 on the r390a. The signal sounds ok, maybe not 599 but usable. Now on to rebuilding the HP-23 ps. Can you tell me how to do that? I might get on t am yet.
Thanks and regards,
Tom N0TJL

ok Tom....sounds like progress .... need a bit more grid current .... have you tried 80 and 40 meters yet ?
will need some relays for the hp23 .... one to turn on the hv and another to step start it as well as the ptt function ... lotsa different ways to do this ... I would avoid using 120 vac for the coils and use a lower voltage ...this is just personal preference

I tried 15M yesterday - almost no grid current at all. I will try 80 and 40 today. My B & W tr switch seems to work also. I bought it at a hamfest years ago in Atlanta.
Tom

I checked 80 and 40 today. 80 showed a grid current of 3ma and a plate current of 100ma. Power was 10w. I reduced the grid current to 2ma and both plate current and output power remained the same. 40 showed a grid current of 0.8ma, plate current of 115ma and output power of 7w.
Regards,
Tom N0TJL

Does someone have a procedure to convert the Heath HP23B from voltage doubler to full wave bridge rectified? Don't want to dive into that ps without some sound advice backing me up.
Regards,
Tom N0TJL

Tom .... I think you are on the cusp of doing great things so have a little faith in yourself and go ....  

to prevent any sort of damage due to error, limit the power to the supply with a series resistor (aka incadescent light bulb) in the 120V ac supply ....notice that when you energize the supply without a load you will see a dull glow in a 100W bulb ...this is normal .... as a quick test intentionally short one of the windings (apply proper safety rules) and note that the bulb comes up to full brilliance but nothing should smoke or pop or other disgusting things .... this is a ballasted test and is recommended for non-destructive testing of new equipment aotbe

Sounds like the light bulb variac that I use when I recap old receivers. Start at 25w and go up to 100w bulb with an old receiver that hasn't been switched on in many years. It can save one from a smoky outcome. Is there a schematic that will show me what the ps should look like?
Tom

I'm not sure that I understand yer question .... I would be looking at the ac supply for the HW and the Heath ps23 and how to add the necessary relays and such

The HW APS-50 ps schematic shows a relay with the coil (battery powered) across pins 7 & 8 and the relay contacts across pins 5 & 6 which connect to the primary windings of the power transformer. My HW xmtr has a battery powered relay installed in it. I assumed that was added later in this xmtr's career when someone else used a nonHW ps and required a relay to operate ptt. The coil of this relay (operating voltage unknown) is wired to a connector on the rear of the xmtr. I vaguely remember reading about an xmtr modification like this but nothing specific was mentioned about the power supply used. That is where I get lost.
Tom

ok .... to focus on the added ptt relay ... look at its coil and the movable armature that is mechanically coupled to the contacts .... where the armature is attracted to the pole of the coil, is there a copper ring ? ... this is an indication of an ac coil if present and if absent, a dc coil ... if dc its probably fairly low voltage and a dc supply can help determine this .... if it has the copper (shading) ring you can use a variac to start low and see where it pulls in .... how many contact sets are available ?

I don't see a copper ring. Probably dc and has two sets of contacts. The manual discusses installing a 6v relay and that is probably what one of the previous owners did. Could I use a full wave bridge rectifier to convert the Heath HP23B? The rectifier is rated at 1000V, 8A or would that cause problems? The HW APS50 power supply schematic calls for a 12MFD 600v smoothing capacitor and a 25k 20w bleeder resistor in the high voltage output (425v 275ma). Would something like that work in the converted HP23B?
Regards,
Tom

sorry ....I've been busy with family stuff

1.  do you have a variable dc supply ?   if so disconnect one side of the relay coil or verify that it goes to the mic ptt switch .... the idea is to isolate the relay coil so that it is the only load ....bring up the voltage slowly and the relay should activate .... note what the voltage is and what current is drawn

2.  yes the full wave bridge capacitor input will yield 300 - 350V ... 1kV piv is a little low but should be ok .... use an appropriate mov or capacitor to snub spikes .... are there any filter chokes ?  they will eat you up on piv

3.  that was because they used filter chokes .... chokes require a critical minimum current to provide voltage regulation .... use a pi section hv filter with a series resistance of 50 ohms or so, 40uf or greater caps will get the ripple removal job done ....look at the Heath DX60 power supply for ideas

Thank you. I have had family visiting over the last two weeks. Granddaughter really wore me out. Fun though. Looks like a wire is disconnected going to the mike connector. Will check it against the schematic then test the relay voltage. I do have a variable dc ps. Can I duplicate the component values in the DX60 ps?
N0TJL

I suppose so ....  the question is not easy to answer because the dx60 is a tapped doubler and your modified hp23 is now a full wave bridge but the components should work since parameters are similar ... when in doubt, Ohm's law is your friend