Yaesu FRG 7000 deaf from 12mz upwards.

[Jazzman]

Hi, firstly I put my hands up and say I know little about electronics as such, but have keen interest in challenges.

So I bought the FRG 7000 locally for £50.00, the guy said it was dead other than all the lights come on and it hisses.
Once I had the cover off I could see it had been well and truly got at in terms of alignment. Each IF can had a penned line on the edge with not one of them lining up.  Anyway to cut the chase;  with nothing much to lose I have painstakingly worked through them guided only by ear, and have reached a point where I can go no further.
I should add I have stripped the band selector and cleaned all the contacts and rebuilt it and all is working well and as it should. 
I have tons of transmissions coming in on LW, MW and all the way up to 40mtr, with loud clear and plentiful sideband transmissions on 40. From then on it gets increasingly quiet.  The peaking of the Mhz control gets more and more difficult , there is no peaking hiss.

So my question is this, given the liveliness and sensitivity up 7 possibly 8 Mhz, what would cause it to tail off so, particularly the peaking of the Mhz control.
What am I missing...apart from equipment like a frequency counter, sig gen and brains etc. ?

Any help appreciated.
Regards.

 

             

[Andy Chee]

Have you got a service manual?

http://www.foxtango.org/ft-library/FT-Library/FRG7700-FRG7-FRG9600/FRG-7000.pdf

[Jazzman]

Hi Andy, thank you for the pdf link.
I do already have the manual for this set, but as I said before am lacking test equipment to do it properly.
I guess what I was looking for was some idea as to why half the set is working so well while the other half was dead.

Regards,
mike.

[PA0PBZ]

It's normal that things go more quiet above 10 MHz and without some tools it will be hard to decide if your rig is performing well or not. Another receiver could help by comparing what you can hear, and a signal generator would be even better. Since this uses a Wadley loop most of the parts (apart from the band selector) are used for all bands so if reception is fine in the lower part most stuff is doing fine. If performance is indeed marginal in the higher part of the spectrum there are only a few blocks where there could be a problem.

 - Band selector, does tuning the coils there make a difference?
 - Pre amplifier, you generally can get away without one below 7/10MHz. Did you check the voltages on Q01 on PB-1781?
 - The mixer (Q02, Q03 on PB-1781) although less likely
 - The harmonic generator, if it does not produce enough signal in the higher spectrum it could give you the problem you see.

Try to understand how a Barlow-Wadley receiver works and you will be more armed to tackle the problem if one exists.

[xrunner]

Hi, firstly I put my hands up and say I know little about electronics as such, but have keen interest in challenges.

So I bought the FRG 7000 locally for £50.00, the guy said it was dead other than all the lights come on and it hisses.
Once I had the cover off I could see it had been well and truly got at in terms of alignment. Each IF can had a penned line on the edge with not one of them lining up ...
           

Oh dear. It sounds like the gorillas got to it. 

What I mean is people who probably don't have a f*cking clue what they are doing. This is one of the worst situations you can find yourself in with a receiver. What I mean is if there was a failure that caused the receiver to lose sensitivity, that's Problem A. Then a gorilla thinks they can fix it by twisting things they can see with a tool (which don't have anything to do with Problem A), they create another Problem B.

And C.

And D ...

IMHO, having repaired and restored many receivers, you are going to have to start at the beginning of the alignment and see what you can find going logically from start to finish. All that requires a certain set of test equipment, so it may not be worth your time and money. Good Luck.

[Andy Chee]

A multimeter, signal generator, and frequency counter, are pretty much compulsory equipment for any radio alignment.

A modern HF radio could possibly serve as a substitute as a signal generator, if you run it at low power into a dummy load, and use an RF signal tap and attenuator made from resistors.

If you have a nanoVNA, you could use it as an RF signal generator, again, you may need an attenuator.

And finally, you could get a cheap MAX2870 RF signal generator from ebay.

[p.larner]

why buy it when you dont have the gear to repair it?,just stops others with the required equipment from saving a classic radio!.

[CJay]

why buy it when you dont have the gear to repair it?,just stops others with the required equipment from saving a classic radio!.

Oh dear, are you envious someone got a bargain and you didn't M3VUV?

[Jazzman]

Thanks for all the replies they all very much appreciated.
The situation has moved on somewhat, in that I have a Malahit DSP2 and thought I'd compare the reception to the FRG.
Transmissions are pretty poor above 12 Mhz at the moment, but I did find some sideband activity on 28mhz, so decided to really focus the FRG to this area.
At first there was little to be heard but after a little adjustment of a particular tuning cap managed to home in on these sideband signals.
That's as as far as I've got at the moment because...I'm waiting on a frequency counter coming in and a VTVM. I'm also pondering on a signal generator.
I'm not worried about the cost of these outstripping the value of the FRG, the fun I'm having is worth every penny.     

Again thanks for the encouraging replies.
Happy Xmas.
Mike.
   

[CJay]

Sounds like you're having a lot of fun and learning too, dunno about you but that's my idea of a good way to spend my time.

If you've got any Arduino (spit) experience then you could build yourself  really simple signal generator using something like an Si5351 breakout board and a cheap Arduino clone board, total cost would be well under a tenner.

It won't be fancy, it won't be calibrated but it will give you a consistent carrier signal the Frog should be able to 'hear' and it should be plenty accurate enough in terms of frequency for hwat you need to do here.

A proper sig gen should include an attenuator but you can realtively easily add a crude one of those to a simple Si5351/Arduino lash up so you can adjust for 'best' signal

[Jazzman]

Thanks for that CJay, and yes I am learning which is amazing at 75 going on 76!
I used to do a bit of basic radio repair back in the days of octal and b9a valves to earn and extra few quid over my day job as a coppersmith.
Incidentally while in the coppersmith job, we used to make waveguides for Marconi who had a depot in the local town (East Ham London).
Anyway one day a guy from the depot came to collect the guides and I got talking to him about shortwave stuff, he said " come up to the depot on Saturday and you can help yourself to anything we have in the dump room."   On that Saturday I came home with a van load of receivers, Avo meters and loads of other stuff. Now that was what I called a proper Xmas present.
I'm not really in touch with solid state stuff, but I do have a basic overview of what's going on and what I'm aiming for.
Ultimately I'm having a lot of fun and that is what is most important to me. If I don't get the FRG to where I want it then hey ho I gave it a good shot and had a good time doing it.   
     

[xrunner]

Jazzman, I forgot I did a restoration of this receiver four years ago and posted a thread about what I did on this forum. Here's the link if you haven't already found it -

https://www.eevblog.com/forum/rf-microwave/yaesu-frg-7000-communications-receiver-restoration/

[Jazzman]

Hi xrunner, I had already read through your entire and very interesting restoration. In fact it was your description of dismantling the band switch that gave me the courage to do mine, and I'm so glad I did.
So I certainly thank you for that. 

All the best.