Jan 13, 2022 Software by admin

This manual is downloaded from the FoxTango site, Yaesu. FRG HF Receiver. Survival Guide. Revision 2 march. If you want to work on your FRG, it is a must to have the manuals and schematics. See: The manuals are very informative and deal. The purpose of this manual is to provide the reader with information critical to the nance of the FRG general coverage communications receiver.

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One of the things I missed on this receivers is a small RIT control or fine tuning, a very handy device when I am listening in on a net or rag chewing Hams. The receiver is very rugged and, normal used, there are not much problems.

YAESU FRG SCH Service Manual download, schematics, eeprom, repair info for electronics experts

The tune voltage is HF decoupled by a 10k resistor and a 22n condenser. There is not much difference between the first and the last receivers, the only thing I saw was a different coupling of the frequency scale to the dial mechanism. The cores are janual interchangeable, so do one at a time. By submitting a comment, you are declaring that you agree with these rules: I have seen all kinds of junky stuff on e-bay, that was tampered with and sold for high prices, to the chagrin of the new owner.

The remaining problem was now the counter and the clock. I have a credo here: When touched with the multimeter probe, the divider switched to the right frequency, so my suspicion of a bad MC proved correct and I ordered a new MC Removing the paint altogether from the sides is also a possibility, it can be done with thinner and rubbing with an old cloth, you have just to be careful with the front itself, the paint there is quick damaged.

Follow closely the procedure in the manual, if the receiver is in a normal condition, the changes should be minor. After rebuilding, I will try some modifications, to improve selectivity and test some ideas of my own, like a clarifier, improve sensitivity for the AM bands and others.


There are some things to know about the frequency display: The source for trouble is the rectifier, who becomes very hot, so hot in fact that in one case the wires to the transformer caught fire, and the condenser exploded.

It seemed to me frg-770 both sideband oscillators were running at the same time, but I could not see how, because the sideband switch was working correctly.

A wire is soldered to the connection of the 10k resistor and the 22nf condenser and is brought out of the VFO, together with the 3 existing wires. I did it this way in a home brew transceiver some 25 years ago, and that worked fine. You agree not to post any material which is knowingly false, obscene, hateful, threatening, harassing or invasive of a person’s privacy. Direct after filling the lines, I sweep the excess paint off with a cloth saturated with white spirit.

While I was at it I measured all diodes and inspected the rest of the board very carefully. If they fail once there can be a reason they fail again in the future, and putting in a socket is cheap and makes life easier when the need arise. Service and User Manual. The only critical part in this mod is the ceramic condenser, it must be a type with a neutral temperature coefficient NP 0, black dot.

I made a truth table of the 6 input pins of the MB, and soon discovered that pin 15 had no true 0 or 1, but had always a voltage of 3.


The displayed frequency was the counter input, without the IF offset of khz, and divided by a factor I cleaned it as far as possible, but the needle stuck every now and then, so I suspected a broken movement, or the coil out of his bearings.

The first 2 transistors of the amplifier were working, but then things went wrong, so I took the board out again to change the transistors, but after close inspection I found that the BIG soldering iron has been there also, and made a short between collector and base of the third amplifier transistor.


A mode switch changes the display for frequency, clock, on-time, off-time and sleep function. While I had the meter out, I searched my junk box, and found a VU meter from an old cassette deck, which was a near- perfect fit.

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I tried it, but was not happy with the look of it, It was no Frog anymore, so I put the filter back. After a squirt of contact spray and working the switch a couple of times, everything worked nice again.

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I use it also for repainting and refill markings on boat anchor receivers, like the RA and Racal. Close inspection discovered some more shorts between solder joints. Your best bet is to obtain a spare set with a defect display or otherwise, and use the good IC.

If you check carefully, use the frg7-700 and the very good circuit description in the handbook to make yourself familiar with the circuits used. This modification is very elegant, because there is no drilling or extra knobs necessary, simply undone if necessary, easy to use and has no side effects in stability of the receiver. Compared with my other FRG, the signals were almost the same strength, so I spent some time to clean the chassis, knobs and front panel, and rebuild the set.

With the help of this guide your Frog can survive the next 20 years and more. If your display goes weak, you can solve the problem temporarily by removing the orange filter in the display window.