The AM Forum
July 23, 2024, 01:50:44 PM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: 1 [2] 3 4   Go Down
  Print  
Author Topic: Questions about the Harvey Wells Bandmaster  (Read 59457 times)
0 Members and 1 Guest are viewing this topic.
AF9O
Member

Offline Offline

Posts: 4


« Reply #25 on: February 22, 2015, 03:36:58 PM »

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
Logged
MikeKE0ZUinkcmo
Member

Offline Offline

Posts: 443



« Reply #26 on: February 23, 2015, 07:58:43 PM »

Here is the original H-W 50D schematic, for use of D-104s and the like.
Logged

Mike KE0ZU

Bold Text and PICS are usually links

https://mikeharrison.smugmug.com/
n0tjl
Member

Offline Offline

Posts: 44


« Reply #27 on: March 11, 2015, 10:16:56 AM »

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 
Logged
N3GTE
Member

Offline Offline

Posts: 105


« Reply #28 on: March 12, 2015, 08:34:21 PM »

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
Logged
n0tjl
Member

Offline Offline

Posts: 44


« Reply #29 on: March 12, 2015, 09:58:14 PM »

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
Logged
N3GTE
Member

Offline Offline

Posts: 105


« Reply #30 on: March 13, 2015, 07:53:51 AM »

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
Logged
n0tjl
Member

Offline Offline

Posts: 44


« Reply #31 on: March 13, 2015, 10:59:23 AM »

On the 50C schematic is the tank coil L15 and is the cold side toward sw4?
Regards,
Tom N0TJL
Logged
N3GTE
Member

Offline Offline

Posts: 105


« Reply #32 on: March 13, 2015, 05:41:54 PM »

Let's go with terminal 5 on the back panel. L-15 is the 2mtr tank coil.
Terry
Logged
n0tjl
Member

Offline Offline

Posts: 44


« Reply #33 on: March 13, 2015, 06:53:39 PM »

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
Logged
N2DTS
Contributing
Member
*
Offline Offline

Posts: 2303


« Reply #34 on: March 13, 2015, 07:20:31 PM »

Milli ampers, not milli watts?
 
Logged
n0tjl
Member

Offline Offline

Posts: 44


« Reply #35 on: March 14, 2015, 11:19:33 AM »

Of course it is ma not mw, don't know what I was thinking about.
Tom N0TJL
Logged
n0tjl
Member

Offline Offline

Posts: 44


« Reply #36 on: March 17, 2015, 09:27:04 AM »

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
Logged
N3GTE
Member

Offline Offline

Posts: 105


« Reply #37 on: March 18, 2015, 05:03:25 PM »

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.
Logged
w4bfs
W4 Beans For Supper
Contributing
Member
*
Offline Offline

Posts: 1432


more inpoot often yields more outpoot


« Reply #38 on: March 18, 2015, 05:36:58 PM »

......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

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
Logged

Beefus

O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us.         Robert Burns
n0tjl
Member

Offline Offline

Posts: 44


« Reply #39 on: March 18, 2015, 09:55:38 PM »

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
Logged
w4bfs
W4 Beans For Supper
Contributing
Member
*
Offline Offline

Posts: 1432


more inpoot often yields more outpoot


« Reply #40 on: March 19, 2015, 08:48:10 AM »

...... 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
Logged

Beefus

O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us.         Robert Burns
n0tjl
Member

Offline Offline

Posts: 44


« Reply #41 on: March 20, 2015, 10:07:46 PM »

How would this look schematically between the output of the CFC and the crystal socket of the HW?
Thanks,
Tom N0TJL
Logged
w4bfs
W4 Beans For Supper
Contributing
Member
*
Offline Offline

Posts: 1432


more inpoot often yields more outpoot


« Reply #42 on: March 20, 2015, 10:27:28 PM »

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






 

Logged

Beefus

O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us.         Robert Burns
KA0HCP
Contributing
Member
*
Offline Offline

Posts: 1185



« Reply #43 on: March 20, 2015, 10:29:37 PM »

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
Logged

New callsign KA0HCP, ex-KB4QAA.  Relocated to Kansas in April 2019.
n0tjl
Member

Offline Offline

Posts: 44


« Reply #44 on: March 21, 2015, 11:04:39 AM »

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 
Logged
w4bfs
W4 Beans For Supper
Contributing
Member
*
Offline Offline

Posts: 1432


more inpoot often yields more outpoot


« Reply #45 on: March 21, 2015, 12:33:31 PM »

probably fry the 6aq5 grid
Logged

Beefus

O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us.         Robert Burns
n0tjl
Member

Offline Offline

Posts: 44


« Reply #46 on: March 21, 2015, 04:53:52 PM »

That attenuator is looking better and better.
Regards,
Tom N0TJL
Logged
n0tjl
Member

Offline Offline

Posts: 44


« Reply #47 on: March 23, 2015, 08:14:04 PM »

Would it be possible for me to breadboard the attenuator until I get the final configuration worked out?
Thanks,
Tom N0TJL
Logged
w4bfs
W4 Beans For Supper
Contributing
Member
*
Offline Offline

Posts: 1432


more inpoot often yields more outpoot


« Reply #48 on: March 23, 2015, 08:43:32 PM »

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
Logged

Beefus

O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us.         Robert Burns
n0tjl
Member

Offline Offline

Posts: 44


« Reply #49 on: March 24, 2015, 03:43:18 PM »

The carbon resistors are on order and I will get on it asap. Sounds like fun.
Thanks,
Tom  N0TJL
Logged
Pages: 1 [2] 3 4   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.045 seconds with 18 queries.