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So, I really don't know much at all about IF circuits but this is a laid back, no hurry project. Its a 5 tube amp, AM radio, mono phono input. I do have the photofact for it. It gives two part numbers Admiral 72B51 and Merit BC-372. I tried to google both a few different times. Its probably me, but that didn't really help. They should be 455kc, and both coils 24.5 ohms dc resistance. I don't see any info on the internal capacitor values. I've got two different thought paths here so I'm having trouble. I've got a component missing from the circuit, clearly a problem. On one hand, it would be great if someone can point me towards where I can get the exact right part. I've had a place called Hammond Manufacturing recommended, but they don't sell to individuals and I guess I'm just not sure what I need to consider in a modern replacement. On the other hand, is there any "give" here? Can I use a 455kc at 13 ohms(I think I could come up with that from the garage) to see if the amp works with the record changer? This is definitely not the only problem with the amp, so I have no idea how this is going to go. Its seen better days. Its been dubbed Admiral Mud Dauber. Restoration is out of my league. If I can bring it back to life, even partially, I'll be happy. Thank you
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A quick plunk of the IF transformer into Google yields 3 of them at Play Things of past...
1461-663 MERIT BC-372 262 KC IF OUTPUT, 5WIRE,1 1/8 1 10.00
1479-074 MERIT BC-372 262KC OUT, W/FIL,1 1/8",6WIRE 1 10.00
1505-855 MERIT BC-372 262KC OUT, W/FIL, 1 1/8,6WIRE 1 10.00
IMHO they will probably be NOS
Gary Schneider
http://www.oldradioparts.com/merit.txt
The Sams should have images of the chassis. What appears missing other than the IF transformer? Possibly a couplate? If so that can be made up with separate parts.
262 IF are generally found in auto radios.
This may be a "plain vanilla" if, no taps or gimmick caps. Scan and post the circuits for all of us to labor over
Yeppers, Merit BC-372 is 112-H6 Miller
See page 32 this pdf:
https://www.americanradiohistory.com/Arc...log-59.pdf
Quote:Can I use a 455kc at 13 ohms(I think I could come up with that from the garage)
Nope, it's not the ohms at all, it is the resonance...
Chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
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I came across the link to Play Things of the past as well, but they are 262kc instead of 455 so that just leaves me more confused. I guess the cross ref on the sams is wrong? I don't know. I'm not aware of anything else missing, but the plastic base of the rectifier tube is broken and multiple pins are bent. I've got a used one but I don't know for sure if its good or not. The plug in chord needs to be replaced, both leads to the output transformer have hacked up insulation with bare wire showing, there are some small tears in the speaker cone. I'll replace at least the filter caps and I just figure who knows what else might be wrong. I'll try to get some pics of the circuit tonight or tomorrow.
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The Merit part number you had provided not only checks with PTOP but also the Merit catalog that I provided a PDF link to...
If there is a still visible part number on the 1st IF run down the same Merit catalog for an Admiral cross to Merit or reference the Sams for the IF #1. If there is a mistake in the Sams odds are it is not twice.
Alternately, use a modulated signal generator, isolate with 50K and force 455 through the 1st IF plate connection. Use a VTVM/DVM with a detector probe or a scope w/detector probe to confirm that the IF is indeed 455-6 or whatever.
Some data is amiss so one has to fall back to basic info to confirm the missing part. To seek a generic part the circuit detector type needs to be known to determine 4-5 or 6 wire connection. Then it is a matter of the correct frequency.
There are other ways to determine the IF, less convenient, a bit risky, all depends on what you have in "instruments" meaning something that can be pressed into service...
Take a pix of the sams in the 2nd IF area, import into computer and draw red notes around what is missing. Do the same but of the chassis same area. Post the pix for further help...
The pix of the chassis will determine the IF mounting.
Most experienced collector/restorers keep a box of IF's, a match for it can be done by eyeball. Measured on the bench with a good chance that it will work...
I am a bit flummoxed that the frequency is not correct, wrong data somewhere.
GL
Chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
Posts: 6
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Joined: Apr 2019
City: Evansville
State, Province, Country: IN
Posts: 6
Threads: 2
Joined: Apr 2019
City: Evansville
State, Province, Country: IN
all right, got that much figured out. but that picture will probably only last a month. I've confirmed the first IF can is labeled with the Admiral number from the sams. As far as special equipment and that type of work, I'm going to need to do some studying and look into getting some equipment first. But this is helping me get a base for what to focus on. Thank you. Do you mean a pic of the chassis from the sams or of the actual amp?
