[ipwizard]

I need some help with my 39-55. I cant get the MC receiver section to respond to any frequency from 355 - 400khz. Someone in the past had replaced the 6J7 with a metal 1620 tube. I looked the 1620 up and it appears to be a direct replacement for the 6J7.

I read through the instructions on setting up the MC section but can't get it to do anything. I'm using my frequency generator to sweep the freq. range.

Some times if I switch the band switch between BC and Remote ( or what ever it says) the 2A4 Thyratron light up but it never switches off.

I haven't checked the voltages yet.

Any ideas.

[Ron Ramirez]

Sounds like you have some serious MC issues. The 2A4G should only fire (light up) when it receives a signal (of the proper frequency) from the MC remote, or from your signal generator.

The little write-up I did on the MC alignment of the 41-616 is also applicable to the 39-55:
http://www.philcoradio.com/phorum/showth...p?tid=4741

My 39-55 chassis has the wire going to pin 8 of the 2A4G, so you can use the alignment adapter in the 1939 models.

I have a complete 39-55 chassis if you need it. Yours for the cost of shipping. I don't mind helping out a brother in need.

Let me know soon...otherwise it's going to the Radiorama meet in Cincinnati where it will be on the FREE pile.

[ipwizard]

Would it be possible to hear or see (eye tube) the RF pulses from the remote using a signal tracer on the RF setting if probing arounf on the 78 tube?

[codefox1]

Still have a few 2A4 yours for the asking if you need.

[w4rtc]

Hi Codefox1
I would like to get one of those 2A4 tubes. Let me know how.
Joe

[w4rtc]

Hi Ron
If no one wants the 39-55 chassis, I am intersested in getting it, let me know.
joe

[Ron Ramirez]

Keith

Sorry, I didn't mean for this thread to turn into a classified ad...

Keith has first right of refusal on the 39-55 chassis. Guy-Incognito is second, Joe (w4rtc) is third. I'll let you guys know once I hear back from Keith.

Anyway...

Yes, I think you should be able to see something at the 78 tube if the MC amplifier is working at all. Each time you dial the remote, you should see a series of quick pulses (the eye tube in your tracer should close and open rapidly).

[Ron Ramirez]

Oh, fyi...ipwizard is definitely getting the 39-55 chassis. Sorry, GuyIncognito and w4rtc...

[ipwizard]

Sorry guys. If I dont end up robbing any parts from the 39-55 chassis Ron is sending me Ill post it up in the for sale section. I do know ill be taking the dial glass for sure and any parts I may need to fix my 39-55 if needed.

Back to the original topic..

I checked voltages and they all are correct or close enough. I did notice that the 2A4G tube started staying "ON" all the time no matter what I did. I even disconnected the Grid and Plate wires on the socket and when I powered the set the 2A4G tube was still "ON". So I swapped it for the 2A4G tube in my 39-116 and now the tube stays off but I cant get it to fire with my signal gen, or the MC remote (tried rotating the freq. adjustment on the remote).

The only way I have been able to get the tube to fire is by touching the ground of my signal gen to the ground of my freq. counter without the positives connected. This must create a bunch of RF noise which the MC control amp picks up and fires the 2A4G.

My best guess now is the MC receiver is so far out of wack that it's "listening" way out of the 355-400khz range. Someone was in this set before me so God only knows how much the control amp coils have been messed with.

[Chuck Schwark]

A dirty/corroded screw threads (poor contact) or "cranked down" trimmer cap could be throwing freq off too.
Maybe some mica is missing/chipped out and the freq goes way up out of range. Mucked coils are probably a good start anyway.

Chuck

[ipwizard]

I cleaned the MC remotes guts and shinned up all the contacts and lubed it. The remote appears to be working but I have no way of telling what freq. its tramsmitting. The 30 tube does light up when dialed.

I'll read though the MC docs again and try to align the coils and see if I can get anything to happen.

[ipwizard]

Made some progress tonight. I was able to get the control amp to respond to my signal generator. Thing is it responded to a freq. way to low about 216khz. I tried to adjust the coils and it didnt make much difference. I also tried setting my signal generator to 375khz and tried adjusting the coils until the 2A4G tube fired which I was able to do, BUT it was not besause it was on freq. with my generator. The tube fired but if i changed setting on my generator it made no difference. So it must be at a spot where its picking up something else around here.

Anyone have any ideas?

it's going to be cool once it works but getting it there is going to be frustrating..

[codefox1]

Will send you a 2A4 tomorrow.

[Ron Ramirez]

I think one or more of the mica caps across each tuned section of the Mystery Control RF transformers may be bad.

As you know, the RF transformers in the Mystery Control section of the receiver are slug tuned. Each tuned circuit has a fixed mica cap across it.

These mica caps were only sealed in wax, making them prime targets for corrosion.

If these mica caps go bad, you won't be able to tune the RF transformer properly.

When I had my 41-616 apart, I replaced the mica cap in the first RF transformer mainly "just because." It seems to work with the new dipped 50 pF mica I put in place of the old one, although as I recall, I think the value of the original may have been closer to 70 pF? At any rate, I had no trouble aligning the Mystery Control circuitry to its original 395 kc frequency (it is stamped with a big 9 on the stepper unit box, meaning Code 9 or 395 kc).

Be aware that the micas in the RF cans of the 39-55 chassis you're getting from me may also be bad.

[ipwizard]

Thanks Ron,

Ill see if I have any 50 or 70pf caps on hand and replace them. Its worth a shot. The cans are not to hard to take out since they have already been out once for the re-wire.