32v2 solid state LV and HV

[W6TJK]

I'm half-way into rejuvinating a 32v2.
Got all tubes in and powered up using variac.
See no filament on HV rect, nor heat from 5z4 LV rect.

open up the back and see a chop-job on the 6v and 5v fil supplies to the HV/LV.
looks like somebody has converted to SS rectifiers.

Also the 6 and 5 volt fils have been seriesed and run into a full wave,
then to what looks like a linear regulator and thence to the remaining RF/AF fil's

the modulators are sitll on their own fil supply from transformer.

Anybody heard of this kind of modification.
what kind of SS replacement for the 5z4 and pair of 5r4's

thanks
tom

[N3DRB The Derb]

yuk.  

I'd be tearing all that mess out of there, cleaning everything up, then putting the rig back to baseline - THEN doing whatever repair or mods you want to do your way. never trust anyone else's repair job unless you know them and know how they roll.

Most of the time, you wind up tearing it all down anyways, so you may as well clear it out and do it right the first time.

[Todd, KA1KAQ]

Discussed this recently with the HUZman. He runs a V-3 and I use a V-2. That 5Z4 is nasty-hot, it'll take the skin off your fingers if you're foolish enough to grab onto it when hot. A better approach would be doing as Derb said - straighten out the mess first, then build yourself a plug-in SS replacement in an octal base from a dead tube. It's on my list of things to do. LV tranny is a known weak point in those rigs, having the scorching 5Z4 bubbling tar out of the laminations is no help.

[N2DTS]

I have a 32V3 that has been solid stated for 30 years with no problems.
But I just used tube base type plugs and built the diodes on them, instead of changing the radio.
Its important to solid state the rig to off load the filament power off the low voltage trans.
The extra voltage seems good for the rig, it has never caused any problems on any of the 32v's I have had.

I hooked up a variac to the HV trans and run my 32v3 at 800 volts.
I rectified the filament to run the mic preamp tube off of to eliminate hum.

I changed the modulators to kt88 tubes in ab1, with a phaze inverter to drive the grids, feedback from the mod trans secondary to the 2nd stage.

I have used the rig as an exciter for the big rigs, so its been on all day lots of times, and I use it as a standalone rig from time to time.
The thing has been 100% reliable, not even a bad tube all this time.

Its stable, it sounds good with just a d104, it always works, so its the last of the commercial ham gear I have.

Brett

[N3DRB The Derb]

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=390086473726#ht_1390wt_941

I'd rather use something like this than js'ing diodes into tube bases or worse sticking them into empty sockets. for 7 bucks, it's just not worth it.

[Todd, KA1KAQ]

So would I Derb, but they haven't been reliably available which leaves the old tube base approach.

These are especially good since he provides the resistor values to get a proper voltage drop close to the original tube.

Good find!

[N2DTS]

I have never bothered with the dropping resistors in anything, one advantage of the solid state diodes is their 'stiffness', why ruin it with resistors?
If your gear is likely to blow up because you get an extra 25 volts, maybe its time to look into its marginal circuits and components.

30 years without a single problem tells the tale, you dont need resistors.

I don't consider it a JS to build my own solid state replacements, I know what I have, and its overbuilt for less money.

The 32v series transmitters are not fragile like most ham gear, I have run mine up to 1000 volts on the plates, had it on all day, made plenty of old buzzard transmissions, made the usual mistakes on tune up, and it just works, not a single thing has ever gone wrong with it.

Brett

[W3RSW]

Any real ham worth his salt can make a very good 5R4, 5U4, 5Z4 etc. replacement complete with plate-line-only fuses, dropping resistor if required or desired, etc.  I even found an ocular cap that perfectly fits over the octal plug. I may superglue it on if it proves ultra reliable over a good length of time.

I've done that in my 32V2 and also lifted the 5 volt winding where it attached to the HV in order to keep HV off the LV multi-purpose transformer. This I've noted in the manual.  I ought to also put a note and diagram along with all the audio mods on a slip of paper on the power supply's back plate or at the very least, inside the cabinet.

I also run the 32v, 75a2a and other stuff from a bucked transformer yielding 115 vac from 120 input.

But I do not run the 32v's HV on the low tap!
I mean enough is enough. They're very strappingly built rigs.

Derb, yer right,
"ya's got to know your dog."

[KM1H]

I recently obtained a V2 and after doing some serious reading and talking to owners a few problems kept popping up.

The driver and mod iron are prone to insulation breakdown as is the B+ winding of the LV xfmr.

Changing over to SS with no other changes will just hurry their demise and removing the rectifier load has no effect on the weakness.

The intelligent approach, IMO, will be to use a bucking transformer to reduce the input to around 110VAC, measure the LV B+, SS it and add a resistor to return to the previous measurement. Putting the diodes and suitably sized resistor in a tube base and having it exposed to air flow should substantially reduce the external transformer temperature.

The alternative is to get quotes on rewinding the transformers. I asked Gary, WZ1M, about this at Nearfest and it aint cheap. Luckily mine are still OK but do show signs of being replaced.

http://members.tripod.com/tubes_tubes_tubes/transformerrewindingservice/
 
Carl
KM1H

[N2DTS]

I would not believe everything someone tells you.
I have had three 32v series rigs, ran them all off 125vac, in the high voltage tap, without any problems for 20 years.
The one I have left has been run at 1000 volts on the plates at times, and have had no problems at all with it for the last 30 years, so much for weak insulation....

I think its all total BS, the low voltage trans was somewhat overloaded, removing the filiment power off the primary keeps it from getting too hot and crapping out.

Brett

[N3DRB The Derb]

there's no hard rules. If the transmitter only got ran by a lil old lady to transmit on her way to church every Sunday, it's not going to show the same weaknesses as a tx thats got 2,000 hours on it. Every rig has weak spots, but on some of them they just dont present themselves yet.

good example is the resistor inside the vfo box of the johnson transmitters - a known weak spot in the design. but lots of them havent smoked yet.

But at some point they will smoke or cause trouble. So yer choice is either a proactive or reactive choice.

[WD5JKO]

open up the back and see a chop-job on the 6v and 5v fil supplies to the HV/LV.
Also the 6 and 5 volt fils have been seriesed and run into a full wave,
then to what looks like a linear regulator and thence to the remaining RF/AF fil's
the modulators are sitll on their own fil supply from transformer.

   Tom,  The whole concept of combining the 6v & 5v windings, making DC for the filaments might sound good, but pulling that off with the original windings, likely only results in more RMS amps on those windings (more heat), and the linear regulator will dump a lot of heat also if going back down to 6.3v DC. I'd carefully look at that design, and if shabby in any way, return the filaments back to stock AC. Being stock is not so bad.

   I bought a swap-fest Gonset G76 with an overbuilt home brew power supply supply. The guy who built it also made 12vdc from the 6&5 volt transformer windings. What a mess design wise yet beautifully done cosmetically. I had to do a lot of work since I had a HOT transformer and about 15 volts DC going to the 12v filaments in the G76.

Jim
WD5JKO

[W3RSW]

Brett, all what you say may be true for the majority of 32v's, but after reading real case histories on a few rigs, better safe than sorry, especially if the fix's are real easy (120vac bucking).

All the HV issues aside, reducing the filament string from 6.8 or 7.0 volts to 6.3 has to be good for the pubes even if you don't 'respect' the rig  

  Perhaps what your saying is that rig survivability is simply a state of mind?  heh, heh.

OK, So a lot of us get peace of mind simply by lowering the AC to designed voltage.  Many poor sob's are getting 125vac these days of "lazy" elect. company operators in an electrically heated world.

[WA1GFZ]

My Viking 2 CDC LV transformer ran quite hot. I solid stated everything and took the two 5 volt windings and put them in series with the LV primary low side (White line cord lead) Now it runs nice and cool. I ripped out the 6AL5 socket and mounted a fuse holder for a fuse on the LV transformer. This dropped the heater voltage from 6.8 to 6.3VAC. My line is usually 126 VAC. My HV is 760 VDC.

[N2DTS]

All that might be so, or it might be the rigs were kept in moist enviroments, or rarely used.
I know someone who has 2 on his basement floor for the last 40 years, never been turned on.
THEY might blow up if used....

I have had 3, I got them for about $50.00 each, so I dont attach much value to them, one was bad on arrival, I was told it had the 'typical' blown low voltage trans, it was actualy a shorted trimmer cap in the multiplier section I replaced, the trans was fine. I got 2 for $90.00, the broken one was supposed to be a spare parts rig...

While I had them, I never had a single problem with any of them after replacing the one trimmer cap.
I used them a lot, but always used them with solid state rectifiers and no dropping resistors, no bucking trans, I have plenty of spare tubes...
I would expect to have something crap out, but nothing ever did, even at 1000 volts on the plates.
30 years is a long time!

I have had lots of vintage rigs and never had a tube crap out, although some stuff came with bad tubes.
I used the r390a for 25 years, other then the clamps breaking, no electrical problems, or tube problems.

So, over such a long time, with so much stuff, without any problems, I don't buy into the hype.

My 32V3 must be 50 years old, its amazing nothing has crapped out, at least while I have had it....
Collins built some good stuff...

Brett

[W3RSW]

Ooooh, your about due for the infamous ceramic tit breakage on the T/R relay trick.
Hex on ya 

Yeah, I agree.  The 32V's are built the way YAm rigs should be 'cept for that tiny relay.

[KM1H]

I would not believe everything someone tells you

I agree but I do tend to believe what many have said. On here you are only that someone as in singular. I also believe Gary who regularly gets various 32V iron in for rewinds.

I prefer to err on the side of caution in this case.

Carl
KM1H

[Gito]

HI

From the ARRL handbook: Current inrush ...,When the supply is FIRST TURN ON,the discharged input Capacitor looks like A DEAD SHORT,and rectifier passes a very high current.it's called I SURGE,some form of protection is usually  necessary to protect the diodes until the input capacitor becomes nearly charged,unless the diode have a very high surge current rating(several hundred amperes).

In Power supply using rectifier tubes the current inrush is limited by the resistance of the coil winding (internal resistance of the transformer) ,the INTERNAL RESISTANCE of the RECTIFIER TUBE ,the internal resistance of the choke and the value of the inductance also The value of the smoothing capacitance,

The difference in SS rectifier ,the internal resistance is small ,only about 0.6 volt drop even with high current flowing.
In TUBE rectifier there's a high voltage drops with a high current flowing in it.Meaning a higher internal resistance.

Conclusion ,
On switch on ,An SS rectifier has a higher Current inrush ,than Rectifier using  tubes  power supply .

Meaning the P.S transformer needs a higher current flowing in it ,than with Tube rectifier  when the PS first turn on
 
So can the Transformer handle this Current in rush in long terms?
So it's Our Choice ,using a small limiting R with the SS.or not,

It's not the operating current on transmitting ,but the Current Inrush when the power supply is first turn on.
Again I can be wrong


Gito
 

[WA3VJB]

I've had my 32V2 for 38 years, and the LV transformer crapped out the first year I had it.

Rewound by a guy in Florida named Jess Price and no problems ever since.

I thought I had caused the crapout by leaving the transmitter on CAL for prolonged periods of time when I was a Johnny Novice. Didn't know any better. It seemed like a good "standby" position.

"CAL" activates the multiplier circuits and the VR tube back by the 5R4s, but the transformer guy, as he unspooled the windings, said he saw uneven pressure in the windings that had actually compressed and deformed turns near the failure point.

So, perhaps a manufacturing error, combined with just the wrong operating environment, add up to the failure mode.

Meantime, I still have just a little bit of anxiety when I bring the 32V2 out for a long ride, but it did just fine on its most recent outing.

http://www.youtube.com/watch?v=iuueqTl0fDo

[N2DTS]

I was on with mine today quite a bit, 800 volts, 180ma, no crap outs!
I admit, I also tack on a 24 uf 1000 volt oil filled off the back terminals for energy storage, with the solid state diodes, no resistors.
So I guess I have the original 10uf plus 24 for 34 uf.
Choke input so inrush current is low...

I checked the audio stuff out, as it did not sound very good in the mod monitor when compaired to the flex, and can't figure out what I was doing with the circuit I added to boost the positive modulation.
Its sort of like a balance control (pot) on the phase inverter to give more drive to the positive modulator tube.
I think I need to redo it, it works but I don't think it was done the right way.

I did a freq sweep, and its about 60 Hz to 10 KHz, the low end rolls off slowly.
 
Brett

[Gito]

Hi

Yes Bret choke input has a smaller inrush current./but still has an inrush current.
But comparing power supply using SS rectifier to Tube rectifier with the same circuit, I think the SS power supply has a higher in rush current than Tube  rectifier.power supply
Because SS rectifier has a small Internal Resistance comparing to Tube rectifier under  load.
And changing the smoothing capacitor with bigger values can change the behavior of the choke input filter.
Just a little thought of me.

Gito

[KM1H]

Gary's comments after taking several xfmrs apart is that the construction, wire and insulation is as low quality as he has ever seen. Perhaps Collins was desperate to keep costs down or maybe they had several suppliers of which one was piss poor.

As I said earlier my V2 has obviously had all 3 replaced at least once and it came with another spare set. Apparently the HV iron is of better quality.

Carl
KM1H

[W6TJK]

Thanks gents.

All input taken with a grain of sand, and swizzle of suds.

Decided to leave as-is and see if SS rectifiers would work.

The LV and HV come up.

Now on to other things...

[N2DTS]

You would think by now, any crappy iron would have failed.
Plus, if something might crap out in my shack, I want to know about it and fix it.


Brett

[KM1H]

If you have a formula for predicting the date of insulation detioration breakdown Im sure we would all like to hear it.

Carl