Yaesu FRG7700 Dial Illumination

[HECTOR63]

I have just managed to purchase one of these receivers but not sure if the main centre frequency dial should be backlit or not? Signal meter and frequency count all good Also has any one any advice on applying an FRA-7700 active antenna unit or FRV-7700 and external monitor speaker to improve internal one which seems fine at the moment.

[Restoration73]

I have owned one since Sept 1983 and it still works. The centre dial is illuminated and
the Service manual details disassembly - you might prefer to use white LEDs be aware
these require a 3V supply. Instructions for connecting accessories are in the manual and
also online. The forward facing internal speaker is fine. I used a Codar PR40 external
preselector for increased gain, powered from the DIN socket.

[HECTOR63]

Many thanks for the reply and advice-I shall take a look into that from now on and see what happens It's a great radio any recommendations for an Aerial? I almost found an FRA-7700 active aerial unit which would have helped greatly as I'm based in a ground floor flat and have only internal usage available so no external wires up the building wall or other aerial systems due to the concerns of the managing agents! Anyway still a good project to get working on and to get the dial lit up again would be good

[g4aaw pete]

From the FoxTango group FRG7700 survival page :-

Dial Lamps:
Dial lamps are long lasting, but they have to be changed now and then. They are 12 Volt /100mA types, with long wires, and can be obtained in every parts store. Eventually you can use bulbs with short wires and solder them to the existing long wires after cutting away the old bulb, using isolation tube or crimping tube to isolate the wires and joints. That way you don’t have to remove the metal front plate for access to the soldering joints.

Be Careful: Remove the power cord first!! The lamp of the VFO is mounted in a small reflector that is very close to the soldering side of the receiving board and this lamp is always “glued” to the grommet from the heat of the lamp, so changing is very difficult. To get access, you have to disassemble the front panel and the analog dial. During the change it is easy to bend the reflector somewhat, and make a short to the board, destroying the counter/clock ic in the process, because the IC (and part of the power supply) is On all the time. It is really necessary to remove the power cord, otherwise you do not remove all the power, with disastrous results.

[HECTOR63]

Many Many thanks PeteSpot on with the glue and wire issues, no probs with the power advices as that would be a very foolish move to even have power to it even when switched off! But I let it sit for about 5 mins before attempting disassembly and gradually found my way round it.Yes its mounted in the said reflector and the glue grommet issue is so old school too. Just didn't want to take a chance on build due to current and voltage as have seen so many other people not checking that issue and either straight away it over heats or after a while and the last thing anyone likes is something or anything smoking!;But the wired bulbs are Widely available as you rightly advised and now I have an idea and voltage and current it will not take long to source some as they are very common and I know what to look for. So mission underway and hopefully back into operation soon, thanks for the advice with the shorts aswell shall keep an eye on that issue but manged to remove the central assembly block without sparks etc and have since powered back up and all's well apart from the said bulb awaiting replacement. In the meantime giving it a good face clean and using some displex to clean and restore the lenses etc as quite foggy and very lightly scuff wiped at sometime but so far so good.

[ChristianFletcher]

Regards antennas I think your going to be limited. May be worth considering some form of stealth antennas as what the management doesn’t see they won’t complain about etc. I hear great things about mag loop antennas but these are very narrow band and somewhat exotic in construction. But they are very goods regards noise rejection which could also be advantageous to your setup. You definitely wants some outside if at all possible

[HECTOR63]

Yes so truemany thanks for the advice and trying various things out and shall take at the mg loops as I have seen those around. Biggest issue is becoming to locate a source of supply for the dial lamp. Most are listed as 'Wheat of grain bulbs' generally about 4mm diameter but I think its a tad smaller and needs better wiring than the Chinese takes on this! I thought CPC or at least RS could help even Cricklewood Electronics appear to be a no show! Anyone have any good places known to try and source?

[g4aaw pete]

Bulbs sold as 'dolls house' lighting might be suitable.
Specifically, the wire ended type.
They may not be 12v but a series resistor will solve that.
I've used them to replace bulbs in my Kenwood R1000.

[Jon_G4MDC]

I might look for bulbs at the railway modellers sites...

[HECTOR63]

Thanks for the replies Folks-but its getting a tad silly now! 4 days and cant find a supplier for a simple bulb! Years ago we used to have everything under the sun when I was working on Car Radios specially for the bulbs as Philips Clarion Alpine etc had all different values and sizes and we had everything! That's all gone now but I shall take a look at the trains thing today. Pete what Value resistor did you use with the Dolls house bulb? Also been advised could use say white LED again what would be the best value to drop the voltage to suit the LED?

[g4aaw pete]

These could be your answer

https://www.ebay.co.uk/itm/8-x-CML-3...4AAOSwkx5XEP5u

I've no connection with the seller.
No current is stated, so suggest starting with a 1k series resistor.

I tried an LED in my B40 dial display. The results were disappointing because the illumination was more of a spot than even / overall coverage.

[HECTOR63]

Spot on Petelooks like the right diameter and the 1k value sounds like a good starting point so have ordered and delivery expected in approx 10days,but at least there's something moving in this direction now and if alls well the stock of bulbs will be very useful. I have scouted around the model railway ideas but 95% of those have gone to LED now to be probably technology consistent with new standards etc expected within there Diorama build's etc.Cheers

[Wendymott]

Not FRG7700. but FRG 7...... I have just replaced the RF Tuning, Main tuning and dial lamps with White Leds.. a bit of a struggle initially, but with a 1K from 10V a MUCH improved display. I use a resistance box to determine led series resistors.. saves faffing..
Well worth doing.

[HECTOR63]

Many thanks for the heads up on the resistance box aswell WendyHave been meaning to get one of those on the bench for years but never got round to it-yes they do save a great deal of 'Faffing Around' too!I have another type of bulb on order with CPC now aswell after finding an alternative to try out but due to Back order is toward the end of the month. Anyway makes more time to get on with other bits and pieces pending but as always one job at a time is always best but for another 2 weeks its going onto the waiting listAlways admired the FRG7 but can never get one to buy as always miss a deal or get outbid on ebayCheers.

[majoconz]

I replaced the lamps in my Sony CRF 5090 with LEDs for a good reason - if you run the radio from the mains then the lamps are on all the time - the scale drum then gets heated and softens and then distorts badly. I installed two white led's back to back so that whatever power was used at the time the led's would light satisfactorily. Regarding the 'spot of light' from white leds - you can file and polish the lens to a wedge shape to distribute the light sideways.

[HECTOR63]

Thanks for the LED advices Martin, but I have some hopefuls on the way now with bulbs as the LEDs thing I think is not really the answer in my case for light dispersal etc. I considered a possible LED strip aswell but shall see what becomes of my trials of the bulbs. Just sad that Yaesu do not appear to be able to support such a simple request for a spare part.

[Wendymott]

Hector. I also chose Leds as with the FRG7 when you switch the dial lights on there is a distinct drop in Line voltage (not measured) but noticable, as lamps take a lot more current. To be honest.. I am not a "purist", if it works I use it
As far as a resistance box goes.... I built my own using 1% resistors and thumbwheel switches...but knowing that decade thumbwheel switches may be harder to find and more costly. My range is 100K to 10 R..... Not being "swanky" but as I had a number of switches I made 2, one has larger 0.5W resistors. But thats what I do..

[HECTOR63]

Many thanks Wendy yes I can understand the points on the Led' s etc so if the Bulbs become a real drama I shall look up some 3-4mm ones with series resistor to suit. Many thanks for the heads up on the Boxes-yes should have done that years ago but there are some Tenma ones for caps and resistor's on CPC at the moment and have also posted wants advice to Dwayne and Beryl at Stewarts of Reading that usually come up trumps with my test equipment needs. They have several listed but awaiting costs-CPC are £40-£60 each for there wares but very modern. If I can find the link I can post if it helps to take a look. There was one on eBay but they want £165!! Tad expensive me thinks.
Cheers

[HECTOR63]

https://cpc.farnell.com/Search?store...t=decade+boxes

Darn it here we are from CPC

[HECTOR63]

https://www.farnell.com/cad/2575612.pdf

From the Cheapest one at the top of the list.