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38-116 updated it works!!!! - Printable Version

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38-116 updated it works!!!! - hotrod - 05-01-2010

While I got the IF transformers out to remove rust and paint the chassis I thought it would be a good idea to test them. However, I'm not really sure how. I have contuniality between terminals 1 and 2 and 3 and 4 on both IF 1 and IF 2. Does it sound like they are okay. By the way this is the Double IF can with the expander unit.


Thanks
Rod

Re: 38-116 IF transformer question - Ron Ramirez - 05-01-2010

Sounds OK to me... Icon_smile

Re: 38-116 IF transformer question - hotrod - 05-01-2010

Thanks Ron, So far so good, I just hope I can get it all back together (lol). I normally don't worry about how the chassis looks but this one was such a mouse house with so much rust I felt I had to do something to it.

Rod

Re: 38-116 IF transformer question - Ron Ramirez - 05-02-2010

Good luck to you, my friend. Don't let that 38-116 intimidate you! Icon_smile

Re: 38-116 IF transformer question - hotrod - 05-02-2010

It not too bad but I really like when I can do the filter caps and then one part at a time. However, I am being triple redundant in keeping track of where the wires go. I am using drawings, tags, and color coding the ends wires with sharpie markers. I didn't attempt to measure the coils in the RF sub-chassis though so I hope they are all good from the few readings I took on the band switch terminals I think things are okay. That reminds me I should also check the output transformer and field coil while I am thinking about it.

Rod

Re: 38-116 IF transformer question - hotrod - 05-02-2010

Oh No, I think my output transformer is bad on the while trying to measure the dc resistance it kept jumping around a little if I move the wires it jumps around a lot and it read rather high. From the center-tap it will read anywhere from 6K to open. The secondary checks out okay at .3 ohm connected to the voice coil but I'm surprised I am getting a reading of only 42 ohms between the primary and secondary. Sound like the primary is shorted to the secondary too me. Anyone know what Universal transformer to get for this as the service literature only gives ohms ready and not impedance information. This output transformer is Philco part number 32-7751.

Thanks
Rod

Re: 38-116 IF transformer (new question Output transformer) - Ron Ramirez - 05-02-2010

From the 1946 Philco Quick Selector Parts Directory:

32-7751

Primary impedance 7600 ohms
Secondary impedance 3.7 ohms
Rated output, watts: 13

The Hammond HX-125E would be a good replacement. If you want a wider frequency response (and want to spend more money), you might consider the HX-1650F.

I've never used any Edcor transformers, but it seems they might be worth taking a look at. They have one, an XPP25-4-7.6K which has a 7600 ohm primary and 4 ohm secondary, 70 to 18,000 Hz response, and only $30.80!
http://www.edcorusa.com/Products/ShowProduct.aspx?ID=366

Re: 38-116 IF transformer (new question Output transformer) - hotrod - 05-02-2010

Thanks Ron, that Edcor transformer sounds like the way to go it has a little better specs than the Hammond 125 series . The 1650 series would probably be hard to mount on the speaker. Also, I did a search on Edcor and seen that Sal gave them a good review on an amp he was working on.

Thanks again
Rod

Re: 38-116 IF transformer (new question Output transformer) - hotrod - 05-03-2010

Well I called Edcor today and they are back ordered 8 weeks on the transformer so I think I will explore other options.

Rod

Re: 38-116 IF transformer (new question Output transformer) - Ron Ramirez - 05-03-2010

Guess the word is out about Edcor transformers! Icon_confused

Rod, did you receive my PM over on that other forum about the PT-41?

Re: 38-116 IF transformer (new question Output transformer) - hotrod - 05-03-2010

Yes I got your PM yesterday and emailed you pics. If you didnt get them check your spam box but I will email with a different email address again just in case.

Thanks
Rod

Re: 38-116 IF transformer (new question Output transformer) - Ron Ramirez - 05-03-2010

OK Rod, thanks!

I apologize, I did receive your email and replied to it. That's what I meant to ask. I just forwarded it to you again. Please let me know if you do not get it.

Re: 38-116 IF transformer (new question Output transformer) - hotrod - 05-04-2010

Ron, I got it last night and replied back. I should mail out the PT 41 on Thursday.

Also, I have a used Hammond 125E on the way that I got for a good price. It is pretty close in size to the original transformer so I don't think I will lose any fidelity.

Rod

Re: 38-116 IF transformer (new question Output transformer) - Ron Ramirez - 05-05-2010

Thanks Rod, I sent you a reply to your email.

And congratulations on finding a 125E for your radio! Icon_smile

Re: 38-116 IF transformer (new question Output transformer) - hotrod - 05-06-2010

Hi Ron,
Got your email today and the PT 41 pack and ready to ship.

I didn't get much done on the 38-116 today because of schoolwork but I did ohm out the power transformer and everything looked good Icon_biggrin I think I got the worst of it licked now I only have 6 or 7 paper caps to replace on the on the Small RF chassis and then finish stuffing one can cap with two 22uf in parallel for the 500V rated caps (Caps 141 4Vand 142). I think I have room to mount a terminal strip for cap 140,140A, 80, 80A, and 80B. I have a 10uf at 500V for 140(the original is 475V) and I think I can get away with 450V caps for the others even though 80 and 80A are rated at 475V.

Rod