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#1
11-07-2020, 08:57 AM
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1969 Bradford AM/FM Stereo Receiver Issues
Hello everyone about a month ago I went though my Great-Grandfather's house to help clean it out to get it ready to sell, and I came across a bunch of old stereo equipment including a 1969 vintage AM/FM Stereo Receiver that was made by Hitachi but was rebadged as W. T. Grant "Bradford".
For some reason or another the left channel won't work on it, which is weird because I can get my signal generator to blow a signal through on the left channel just fine in the tape and phono mode by hooking directly to the respective input connections inside the radio, but when you hook a signal source directly to the RCA inputs on the back, the left channel won't work, it won't even work in tuner mode, with the exception of if I tune into some loud static or hash noise on the AM Band, then it will work in both channels but if its actually a station tuned in, then nothing will come out of the left channel, just the right channel, even in FM Stereo mode. Any ideas as to what's going on here? Thanks for your help. Picture of the unit in question posted below. Last edited by vortalexfan; 11-07-2020 at 09:08 AM. 
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#3
11-07-2020, 03:31 PM
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As for the pots I cleaned them several times already to no avail. I even replaced the output transistor coupling caps, and still no dice. I realize this is a lower end unit but this was my great-grandfather's stereo so that's why I'm trying to fix it up. So I can use it with my old reel-to-reel tape recorder.
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#4
11-07-2020, 06:41 PM
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Be sure to clean the function switch real good.
After that its a case of injecting or tracing signals. After the pre amps there will be a coupling cap to the PA's. From that point everything is direct coupled so things get a little more tricky. Run it a few minutes & see if either channel is getting hot. When outputs short often the "bad" channel sounds better. The "good" gets low B+ & barely works. Confusing ! A manual would be nice but in the amps the mirror image makes things quite doable. BTW with direct coupled PA's its best to change all semi's & lytic caps in the bad stage. If you leave a leaky transistor behind everything goes again. Especially on high power amps. Takes a microsecond to blow everything out again. 73 Zeno  LFOD !
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#5
11-07-2020, 07:06 PM
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Well the mode switch I've tried to clean 4 times already, and I'm still not getting anything out of the left channel. I have a picture of the amplifier board below so you can see what it looks like. This thing does have a power transformer inside it, which is kind of unheard of for some of the lower end receivers from that time period, which means this was probably a decently made lower end unit, and the case is made of real wood, which means that this was made before they cheapened these things up by eliminating the power transformer and going to faux wood cabinets. Like I said, I don't think the amplifier is the issue otherwise I wouldn't of been able to get a signal from my signal generator through.
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#6
11-07-2020, 09:59 PM
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OK well I think I may have figured out part of the problem, although I'm not sure if this is what's causing the problem or not, but I was looking over the amplifier board carefully observing the parts making sure that each side was a mirror image of each other and I noticed that on the working channel (the right channel) side of the board is missing an electrolytic cap.
There's supposed to be 2 100 MFD 16 V Electrolytics towards the front side of the amplifier board and there's only one on the right channel side and there's 2 on the left channel side, and the missing cap on the right channel side looks like it might of been cut out for some reason because it still has a little bit of the (+) lead sticking out of the board yet while the negative lead is completely gone. I also noticed a missing resistor in the non-functioning channel (the left channel), and looking at the resistor's color code on the one that is still in the circuit on the working channel it appears to be a 77 Meg resistor (3 Violet stripes), which seems like an awfully specific value of a resistor. I have a blown up picture of the area in question below with the missing cap and resistor marked in the picture. What do you think? Am I onto something?
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#8
11-08-2020, 11:04 AM
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#9
03-16-2021, 06:26 PM
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A little Update on this Stereo:
I was able to get it going, it was a case of bad 2SC828 and 2SC458 transistors in the amplifier section. The only issue I'm having now that in FM Stereo Mode the left Channel is very distorted and the right channel is fine, but its fine in FM Mono mode and AM Mode and Phono and Tape mode, its just FM Stereo Mode that is having troubles right now. Any ideas as to what that's all about?
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Linear Mode
