Bush TR82C VFO Frequency - UK Vintage Radio Repair and Restoration Discussion Forum

RobinBirch · 22nd Oct 2007, 10:14 pm

I've had a TR82C kicking around for ages which I finally thought that it was time I had a go at it.

Replaced the old electrolytics and checked all the voltages, all within a tenth of a volt of where they should be so why no signal. Um, Put 470 kHz into IF chain - nothing. Tweak slugs, nothing. Play with sig gen - IF chain is set up to about 530 kHz and no slug tweaks will get it very far from that.

After realising that I set the IF chain up for the lowest frequency that it would tune to, about 520 kHz and then set the mixer osc to that.

Obviously I have now lost part of the bottom of the MW band and when I try to set the LW band up then it is all off to one side - heigh ho.

Any ideas as to why the IF chain is where it is, I can't see anything obviously wrong. Would it be possible to tune the coils to somewhere else by changing the caps around them or am I doing something stupid?

Robin

Station X · 22nd Oct 2007, 10:26 pm

Is it possible the slugs have been replaced with some made from a different material? Say ferrite replacing iron dust or vice versa.

Changing the value of the capacitors across the IF transformer winding will change the IF, but this can be a difficult job if they're inside the cans.

I hesitate to ask, but is your signal generator calibrated correctly?

Steve_P · 22nd Oct 2007, 10:28 pm

The IF is 470kHz. Why it's at 530kHz god only knows.

If you've not got the manual, you'll get it by clicking top right. Then follow the setting up procedure.

If it won't come in at all, then check the caps are the ones specified.

Cheers,

Steve P.

Darren-UK · 22nd Oct 2007, 10:48 pm

Quote:

Originally Posted by Station X

Changing the value of the capacitors across the IF transformer winding will change the IF, but this can be a difficult job if they're inside the cans.

I recall someone, quite a while back, having a similar problem with a Roberts R200 or R300. After much banging of head against wall it turned out the problem was indeed one of those little caps inside an IF can. In the TR82 I think these caps are 200pF and 400pF - not certain without looking it up.

I was also wondering about the slugs. Correct type ? are they all intact ? I once had a weird IF problem in a Perdio and found the cause to be one of the slugs which had, somehow or other, partially disintegrated at its inner end inside the former

RobinBirch · 23rd Oct 2007, 10:45 am

Thanks for the advice.

The possibility is that one of the slugs has disintegrated as there is one in the last IF/AM detector that won't budge and feels rough at one end.

I set it up starting at the last IF can and this was the one that wouldn't move to 470 kHz so that would make some sense. In a day or so I will carefully remove the slugs in the last can and see what I am looking at.

The sig gen is probably a lot more accurate than most - it's a marconi comms set tester, a very nice 400 kHz to 300 MHz AM/FM/Phase modulation with built in AF/RF power and distortion measurement.

"Click in top right hand corner" of what?

Cheers

Robin

RobinBirch · 23rd Oct 2007, 10:47 am

Oh, looked at the web page - see what you mean. I've got the service sheet in the pile of red TV and Radio servicing books that I've got. Doesn't give much in the instructions other than the numbers but it is enough to check that the circuit is ok.

Robin

RobinBirch · 23rd Oct 2007, 11:35 pm

Ok,
I know what's going on now, some one has been here before :-(. About half of the slugs have disintegrated and several of them don't look like they belong here :-(, different sizes and threads.

So, I have got together enough good slugs to do the 2nd and 3rd IF and AM detector. All tune nicely on 470 kHz

.

I do not have enough slugs for the 1st IF and the local oscillator. So, anyone got some dust slugs suitable for a TR82 that I could scrounge/purchase.

Looking at it I think someone has had a play, screwed up and tried to recover by putting in whatever slugs were to hand and they were the wrong type.

I think I need 3 slugs, two for the IF and one for the LO.

I will also post this in the wanted section.

Cheers

Robin

RobinBirch · 29th Oct 2007, 9:06 am

Good news,
Job done. Thanks to Mike Nobel who sent me a set of slugs and Ed Dinning who offered help.

Mike's slugs turned up on Saturday and I fitted them last night with a crude set up and then trimmed it up this morning - works a treat. I now have a nice clean working TR82C

Now, where's that 208 luxembourg station gone

Cheers

Robin

22nd Oct 2007, 10:14 pm	#1
RobinBirch Hexode Join Date: Apr 2003 Location: Cotswolds, UK. Posts: 465	Bush TR82C VFO Frequency I've had a TR82C kicking around for ages which I finally thought that it was time I had a go at it. Replaced the old electrolytics and checked all the voltages, all within a tenth of a volt of where they should be so why no signal. Um, Put 470 kHz into IF chain - nothing. Tweak slugs, nothing. Play with sig gen - IF chain is set up to about 530 kHz and no slug tweaks will get it very far from that. After realising that I set the IF chain up for the lowest frequency that it would tune to, about 520 kHz and then set the mixer osc to that. Obviously I have now lost part of the bottom of the MW band and when I try to set the LW band up then it is all off to one side - heigh ho. Any ideas as to why the IF chain is where it is, I can't see anything obviously wrong. Would it be possible to tune the coils to somewhere else by changing the caps around them or am I doing something stupid? Robin

22nd Oct 2007, 10:26 pm	#2
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Bush TR82C VFO Frequency Is it possible the slugs have been replaced with some made from a different material? Say ferrite replacing iron dust or vice versa. Changing the value of the capacitors across the IF transformer winding will change the IF, but this can be a difficult job if they're inside the cans. I hesitate to ask, but is your signal generator calibrated correctly? __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

22nd Oct 2007, 10:28 pm	#3
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Bush TR82C VFO Frequency The IF is 470kHz. Why it's at 530kHz god only knows. If you've not got the manual, you'll get it by clicking top right. Then follow the setting up procedure. If it won't come in at all, then check the caps are the ones specified. Cheers, Steve P. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

23rd Oct 2007, 10:45 am	#5
RobinBirch Hexode Join Date: Apr 2003 Location: Cotswolds, UK. Posts: 465	Re: Bush TR82C VFO Frequency Thanks for the advice. The possibility is that one of the slugs has disintegrated as there is one in the last IF/AM detector that won't budge and feels rough at one end. I set it up starting at the last IF can and this was the one that wouldn't move to 470 kHz so that would make some sense. In a day or so I will carefully remove the slugs in the last can and see what I am looking at. The sig gen is probably a lot more accurate than most - it's a marconi comms set tester, a very nice 400 kHz to 300 MHz AM/FM/Phase modulation with built in AF/RF power and distortion measurement. "Click in top right hand corner" of what? Cheers Robin

23rd Oct 2007, 10:47 am	#6
RobinBirch Hexode Join Date: Apr 2003 Location: Cotswolds, UK. Posts: 465	Re: Bush TR82C VFO Frequency Oh, looked at the web page - see what you mean. I've got the service sheet in the pile of red TV and Radio servicing books that I've got. Doesn't give much in the instructions other than the numbers but it is enough to check that the circuit is ok. Robin

23rd Oct 2007, 11:35 pm	#7
RobinBirch Hexode Join Date: Apr 2003 Location: Cotswolds, UK. Posts: 465	Re: Bush TR82C VFO Frequency Ok, I know what's going on now, some one has been here before :-(. About half of the slugs have disintegrated and several of them don't look like they belong here :-(, different sizes and threads. So, I have got together enough good slugs to do the 2nd and 3rd IF and AM detector. All tune nicely on 470 kHz . I do not have enough slugs for the 1st IF and the local oscillator. So, anyone got some dust slugs suitable for a TR82 that I could scrounge/purchase. Looking at it I think someone has had a play, screwed up and tried to recover by putting in whatever slugs were to hand and they were the wrong type. I think I need 3 slugs, two for the IF and one for the LO. I will also post this in the wanted section. Cheers Robin

29th Oct 2007, 9:06 am	#8
RobinBirch Hexode Join Date: Apr 2003 Location: Cotswolds, UK. Posts: 465	Re: Bush TR82C VFO Frequency Good news, Job done. Thanks to Mike Nobel who sent me a set of slugs and Ed Dinning who offered help. Mike's slugs turned up on Saturday and I fitted them last night with a crude set up and then trimmed it up this morning - works a treat. I now have a nice clean working TR82C Now, where's that 208 luxembourg station gone Cheers Robin