Golborne Vintage Radio

Full Version: FRG7 mod
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When I was a nipper and in shorts, I was loaned a Yaesu FRG7 (frog) and spent many a happy hour scanning the wavelengths. It was a sad day when it had to go back, and I really missed that radio.

Fast forward many years, and with gelt in my pocket a FRG7 came along my way.  As usual with me, I buy things, put them on the "Rountuit" list and often forget about them.

I dug the radio out as I had recently been doing some aerial work and after a brief de-dust and internal inspection of the capacitors which were still in good condition and doing what they should be doing, she was plugged in. Again,old capacitors from the 70s and 80s are often fine but the mid 90s onwards examples often go futt with time, which says alot about modern manf methods, obsolesence built in. 

One annoying bug with the frog, is that of the lock LED on the front panel which indicates if the internal synth is correctly set. However, on the frog, this is not intuitive in that the LED lit means out of synth and LED out means correctly set.  A search on t'net found a mod for the frog in which the original red LED is replaced with a bi colour red/green example and a handful of parts on a pcb provide the switching.  First attempt at fitment was a bust, I had mounted the pcb topside and for some reason the circuit board was causing interference. Closer inspection of the document revealed in a small picture that the author had mounted the pcb to the underside, just behind the tone switches and on re-location of the pcb to the position all was well.

So, with mod carried out and tested, it's back to listening.
I have a frg 7 which works well. The LED light does function in an odd manner with good lock being light off rather than on but I'm used to it and it doesn't bother me. One odd fault I have at the moment is the dial light when turned on sometimes appears to have a total or partial short as the set dies and the dial light barely glows. Turn the light off all is well. I had a quick look and couldn't see any obvious fault but need to have a proper dig around. I think there is an LED panel light conversion so maybe that's the easiest option.
The lighting on these sets is pretty simple, just 12v grain of wheat bulbs with a limiting resistor. Worth checking if the set dies with the main lights illuminated or if the ones in the tuning drum make the set die with the switch in a particular position.
Terry.

Attached are four jpegs of the schematic for the FRG7, as you can see the wiring for the lights is pretty simple.
Thanks Ed. I actually have the original manual/operating instructions with the circuit diagram. When I did have a look at the lights I did trace the lighting wiring and all seemed well. The annoying thing is when I took it out the case it worked perfectly and did for a while after but now it's resumed the fault. It's hard to trace a fault when its intermittent. It happens all the time and doesn't matter which band I'm on.
Surely there must be a simple wiring fault perhaps caused by the panel screws being wrong as in too long. Ambient light problems went away when OC71 transistors stopped being used in mainstream equipment.
One to check Ed. There is a pinch point in the cable loom where the case slides on, directly over the top of the tuning barrels. About 3" worth of wiring running in a spot where it will abrade, and all lighting cable.
One other little mod came my way. The fitment of a 100R resistor between the SW1 and BC connectors on the rear apparently allows the use of the frog on all frequencies via the PL259 and to do away with the long wire.

One to test later.
Anyone know of a reputable repair shop to line my Frog7 up ?. Just had it re capped by a tv repair shop but they were unable to do the lining up of the receiver .
Seems strange that they don't, apparently, seem to have a signal generator? Doesn't sound very 'reputable' to me but then, there are bad reputations as well as good ....
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