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Hello Everyone,

I just acquired a broken FRG-7. I bought it untested for a decent price.?

After it arrived I tested it and confirmed my suspicions that the unit was not functioning. It appeared to lock correctly, tuning the MHZ dial the lock light functioned correctly but there was no readout on the S meter, and peaking with the preselect did nothing.

I opened it up and found the previous owner had butchered the RF board, attempting to replace the front end transistor trying to swap it for an NTE 454. An attempt was made to solder the leads of the 454 to the old leads of the old front end transistor, the previous owner trying to use what I assume was plumbing solder. I removed all the butchery and hooked the NTE 454 up correctly.

The receiver started to work immediately, and I was able to tune and peak on all bands. It was on for a few minutes while I tuned around the bands early in the day. I was able to get the BBC and several time signals. Turning the unit off and coming back to it a few hours later the lock light was stuck on, the receiver completely deaf in the front end. The lock light would only turn off when setting the MHZ dial to the lowest frequency.

I read the manual, on this issue and took note of where VR102 was set, ans rotated it around a few times. I also used contact cleaner on all the switches, power switch, band switch, mode and VR102, still nothing. Lock light is stuck on. I turned it off and turned it back on and BOOM! It's working again! I let the unit run for 4 hours listening to all sorts of shortwave programs. Switching After 4 hours I turned the unit off and then immediately back on and the lock light is stuck again.?

Anyone have any idea what could be causing this behavior? The unit once working works flawlessly for hours, but it will then refuse to work at random, requiring random amounts of turning off and on again? I did read the PSU and its outputting high at 15.9 volts. Could the electrolytics in the PSU and AF board be causing power issues causing the receiver not to lock?

Let me know what you think

My first guess is the loop section is randomly going into oscillation. Is there any sign the previous owner has "adjusted" any of the tuning coils?? Next time the light wont extinguish, carefully try tuning one coil off resonance to see if effects the symptoms. If so, it is reasonably easy to retune these correctly. These coils are in a row on the right? hand side of the RF board.? The first signal IF are the coils on the left. Also check for any damaged components in that area,? especially bypass capacitors. This stage operates at around 55 MHz with very high gain.

Thank you Pentagrid for your quick reply. I think you might be onto something. The set functions very rarely I've only gotten it 3-4 times out of dozens of tries. I'll talk more in depth now about issues as I didn't want my first post to be too wordy.

I did notice that sometimes when the set was functioning it would almost sound like it was entering regeneration like a Regen set. It would be very slight, but it would start to oscillate very slightly and was very easy to tune out and back on frequency and have it disappear. This only happened once or twice in 6-7 hours of listening. The receiver remained extremely stable throughout the sessions I had it going.

The owner whilst butchering the RF board was not shy with the plumbing solder and made a mess, solder did drip on a couple components. What was easy to clean off (solder blobs stuck to the board for example) I removed. I got all the solder off except on 2 parts. It got onto 1 capacitor, but seems to be electrically isolated. I will probably replace this capacitor, as I feel like this will affect the function and possibly allow signals to enter/leave. The part I am majorly concerned about is L101. The previous owner allowed a solder blob to make it onto one of the windings on the coil. The coil still has good continuity, but the solder also has continuity to the rest of the coil. This coil either needs rewinding or replaced, as sections of that coil are probably bypassed by the solder. I anticipated needing to replace that coil before the set was working at all, but was surprised when it started to work and work well on what seemed like all bands.

Does anyone on here have a source for L101 for the RF board, or any advice on whether this solder blob on L101 would affect the radio in the way I am describing? I am not familiar with the way these sets function. I will most likely try to wind a new L101 or try to find a replacement even if this not the root of my problem, but I would like to avoid buying a whole other FRG7 to save this one, as this one isn't in the best shape as you can imagine.

NEVER? get? a hot air gun near these old circuit boards. These boards are very poor quality by modern standards and the tracks will be damaged very easily..

L101 is the low frequency RF tuned circuit, so is not the cause of the problem you describe. This tuned circuit is only used to peak the front end used from 500kcs through to around? 1800kcs.
Ideally, you would connect an oscilloscope to? TP109 and monitor? the waveform. This should rise and fall smoothly as the MCs control is adjusted through its range.
.........

Thanks again everyone for the responses.?

I do not own an oscilloscope, been meaning to get one for some time now. I think that is the only way I can get further diagnosing, as I am not used to transistor gear or wadley loop receivers, I have only repaired tube gear and built Regen receivers before, never toyed with something like this. I only own several DMMs, a VTVM and a basic Heathkit analogue RF generator.?

An update on where I am at right now - I removed all the solder off the board besides the blob on L101. The remaining blob was on c117 next to T05 and T06 and was not electrically connected. I am glad that coil L101 is not critical for SW listening. I was not looking forward to winding a coil that small.

The receiver has not worked at all since my initial post. I will better describe the behavior here:

The lock light only goes out when the MHZ dial is tuned to 0, peaking in noise to the right of the 0. The light however will not go out when the band switch is set to the AM band, only on bands 2-4. The preselect still does not seem to have any affect on this. I do get S meter movement when tuned here.?

I will see if anyone local has an oscilloscope I can borrow, or maybe look at getting a used one.?

I will try reflowing the board as suggested, in particular I will focus around the IF cans. I will only use a soldering iron because as Pentagrid pointed out old PCBs are fragile and not up to the task. I plan on working on different parts of the board simultaneously to spread the heat out better.

Any other suggestions before I look for an oscilloscope?

Here is a simple realignment method requiring few test equipments.

https://worldradiohistory.com/UK/Short-Wave-UK/80s/SWM-1981-10.pdf?