Beloved Tandberg Series 15 - Page 4 - UK Vintage Radio Repair and Restoration Discussion Forum

Paulus.d · 9th Jul 2009, 10:18 am

I have now used the 'Big' drawing to list all the caps used in this baby!

Will 2.2uF do instead of 2uF? Also will 82uF work in place of 80uF??

If so, then I'll replace ALL of them....

Paulus.d

ben · 9th Jul 2009, 11:26 am

Quote:

Originally Posted by Paulus.d

Will 2.2uF do instead of 2uF? Also will 82uF work in place of 80uF??

yes. should be fine. let us know how it goes...

Paulus.d · 13th Jul 2009, 5:46 pm

Went back to LZ-34 & LZ29 for a time but I am a little disappointed with the LZ-29 (see my other thread) so I'm back with this one again.
Reviewed all posts again - I must admit i am worried about the post where the voltages wered discussed, I claimed the main transformer was putting out 28-29v AC, on the diagram this should be 40v... I'm I missing something here? If the rectifier is put back in circuit and the first stage of the power supply, it reads 28 point something volts DC at point 18 on the diagram, again where the diagram states 40v

It's a pity the PCB's are out of the unit waiting for the caps or i'd put them back and meter again and maybe change the transformer to one that outputs 40v

Best wishes
Paul

Steve_P · 13th Jul 2009, 5:57 pm

Do you get 24v at point 6?

Cheers,

Steve P.

Paulus.d · 13th Jul 2009, 6:00 pm

Yep, according to my own post 24.4v, so basically it doesn't matter about before that point?

Regards Paul

Steve_P · 13th Jul 2009, 6:05 pm

Finish doing all those caps and put it together again. Then we'll see what it does or does not do.

Cheers,

Steve P.

Paulus.d · 13th Jul 2009, 6:08 pm

good idea, Jezzer3 just got back to me about them so hopefully get 'em in quick......

Regards Paul

Paulus.d · 25th Jul 2009, 5:16 pm

15 electrolitic Caps replaced and Pcb's back in......I didn't replace them ALL though....

Anyway, switched it on...turned it up and.......

B-B-B-B-B-B-B-B - still there..

I am a bit depressed now. thinking of getting another machine to swap with....

Paulus.d

Steve_P · 25th Jul 2009, 5:31 pm

Clean all the switches again and again.... make sure they are clean.

I'll have a think.

Cheers,

Steve P.

Paulus.d · 26th Jul 2009, 11:07 am

yes, all cleaned again before putting it back together!
My recent rethink with the volt readings probably means I'm going to borrow my brother in laws variable power supply, he's a tattoo artist, and disconnect the main dc at rectifier and feed it from this - just to rule out the transformer and rectifier.

Other than that I'm lost - apart from replacing everything passive, all the caps and resistors, I just don't know what to do. Perhaps a call to the members for anyone with spare PCB's for one of these or get another Tandberg.....

Regards
Paulus.d

DOFFERY · 27th Jul 2009, 5:53 pm

Hi Paul,
As you seem to have replaced almost the whole set & checked the voltages have you tried the quiescent current, measure across R133 no input , should be abut 16mv D C, adjust with R 129

Colin.

Paulus.d · 3rd Aug 2009, 9:06 pm

Back now after sound engineering on high school musical in canterbury, uk.

I have got a 0 to 30v power supply - will connect it to PCBS at the rectifier, I MUST rule out the transformer, it's AC volts test at lower than the 40v. So will connect tomorrow and try it.

Paul

af024 · 3rd Aug 2009, 10:04 pm

For what it's worth, mine produces exactly the same racket when the AMPLIFIER/PLAYBACK/RECORD switch is knocked. Perhaps you are getting the same?

Regards,

Andy

Paulus.d · 4th Aug 2009, 10:54 am

Your problem sounds like the switch. I've cleaned mine again and again to no change so I believed a cap was going down in the power supply. Does yours motorboat as described on this thread

Its like a hum that builds up as you turn the volume up then it goes B-B-B-B with the lamps dimming

If its like that too then we'll go back to the drawing board!!!

Regards Paul

af024 · 4th Aug 2009, 6:32 pm

I guess so. I do have to get the switch in precisely the right (wrong?) spot for it to do it. I don't relaly want to turn the wick up to see if the lamp dims at high volume, but I guess it would.

I'm not saying that it definately the switch in your case, just that the symptoms seem very similar.

Best of luck,

Andy

Paulus.d · 4th Aug 2009, 7:01 pm

Tried an external power supply on the AMP - so I disconnected the AC side of the rectifier and soldered 2 wires to the DC power input at the point they join the 2 large caps.

IT'S STILL GOT THE SAME PROBLEM!!!!!

Only having a 0 to 30V supply I started at low volts and turned up. With the supply on full 32.6v the humming cuts in much earlier. Lower that voltage and it gets better at 16.6v any lower the sound stops completely.

This note to Andy - if it's similar to yours then my switch must be ******** and I just can't spot it! I've now got to put the AC side back so I can test out some more theories, including the switch again. Perhaps I'll play with the contacts and see what happens...

Stay tuned for the next exiciting episode!!!

Paulus.d

af024 · 4th Aug 2009, 7:56 pm

Keep chomping at the bit Paul,

We are all eager to know what's going on here ...

Regards,

Andy

Paulus.d · 4th Aug 2009, 8:48 pm

thank you for having faith in me........

Also, as I have replaced caps already, I now know the caps I took out are OK - so I'll be using some of them to replace the caps I didn't swap!!!!!

As already mentioned on the thread - if the lever is pushed into AMP and an input provided, the unit does not do the fault, if you push lever to record the monitor output does not do the fault - in both cases the MIC or RADIO input is fed directly to the AMP PCB bypassing the pre-amp board. therefore that PCB will take most of my attention, strangely thats the one with the AMP-PLAY-REC slide-switch!

Regards PAul

The General · 5th Aug 2009, 8:26 pm

Now I've got one of these, the half track version.
The things which are worth checking at this stage are the earths. There's a lot of gain in this machine (especially in playback) & Tandberg carefully seperated the low- & high-level parts of the circuit to avoid earth loops & feedback.
If you look at the circuit, the power amp & regulator are grounded via the heatsink, whereas the low-level high gain bits are all grounded at one point via the body of the microphone socket. The impedance between these two points needs to be very low. So check that the microphone socket is firmly fixed to the chassis top plate with no corrosion, similarly the heatsink onto the main chassis, also check the chassis top plate is firmly bolted to the main part of the chassis.
Worth checking to eliminate the possibility of poor grounds exacerbating your problem.
Cheers,
Mark.

af024 · 13th Aug 2009, 6:07 pm

Does anyone have a close-up and sharp photo of the AMP/PB/REC switch (both sides of the contacts) that they could post?

Let's have a look at how it looks, number of contact and where positioned and compare it with our own machines.

Regards,

Andy

9th Jul 2009, 10:18 am	#61
Paulus.d Hexode Join Date: Mar 2008 Location: Margate, Kent, UK. Posts: 355	Re: Beloved Tandberg Series 15 I have now used the 'Big' drawing to list all the caps used in this baby! Will 2.2uF do instead of 2uF? Also will 82uF work in place of 80uF?? If so, then I'll replace ALL of them.... Paulus.d

13th Jul 2009, 5:46 pm	#63
Paulus.d Hexode Join Date: Mar 2008 Location: Margate, Kent, UK. Posts: 355	Re: Beloved Tandberg Series 15 Went back to LZ-34 & LZ29 for a time but I am a little disappointed with the LZ-29 (see my other thread) so I'm back with this one again. Reviewed all posts again - I must admit i am worried about the post where the voltages wered discussed, I claimed the main transformer was putting out 28-29v AC, on the diagram this should be 40v... I'm I missing something here? If the rectifier is put back in circuit and the first stage of the power supply, it reads 28 point something volts DC at point 18 on the diagram, again where the diagram states 40v It's a pity the PCB's are out of the unit waiting for the caps or i'd put them back and meter again and maybe change the transformer to one that outputs 40v Best wishes Paul

13th Jul 2009, 5:57 pm	#64
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Beloved Tandberg Series 15 Do you get 24v at point 6? 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...?

13th Jul 2009, 6:00 pm	#65
Paulus.d Hexode Join Date: Mar 2008 Location: Margate, Kent, UK. Posts: 355	Re: Beloved Tandberg Series 15 Yep, according to my own post 24.4v, so basically it doesn't matter about before that point? Regards Paul

13th Jul 2009, 6:05 pm	#66
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Beloved Tandberg Series 15 Finish doing all those caps and put it together again. Then we'll see what it does or does not do. 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...?

13th Jul 2009, 6:08 pm	#67
Paulus.d Hexode Join Date: Mar 2008 Location: Margate, Kent, UK. Posts: 355	Re: Beloved Tandberg Series 15 good idea, Jezzer3 just got back to me about them so hopefully get 'em in quick...... Regards Paul

25th Jul 2009, 5:16 pm	#68
Paulus.d Hexode Join Date: Mar 2008 Location: Margate, Kent, UK. Posts: 355	Re: Beloved Tandberg Series 15 15 electrolitic Caps replaced and Pcb's back in......I didn't replace them ALL though.... Anyway, switched it on...turned it up and....... B-B-B-B-B-B-B-B - still there.. I am a bit depressed now. thinking of getting another machine to swap with.... Paulus.d

25th Jul 2009, 5:31 pm	#69
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Beloved Tandberg Series 15 Clean all the switches again and again.... make sure they are clean. I'll have a think. 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...?

26th Jul 2009, 11:07 am	#70
Paulus.d Hexode Join Date: Mar 2008 Location: Margate, Kent, UK. Posts: 355	Re: Beloved Tandberg Series 15 yes, all cleaned again before putting it back together! My recent rethink with the volt readings probably means I'm going to borrow my brother in laws variable power supply, he's a tattoo artist, and disconnect the main dc at rectifier and feed it from this - just to rule out the transformer and rectifier. Other than that I'm lost - apart from replacing everything passive, all the caps and resistors, I just don't know what to do. Perhaps a call to the members for anyone with spare PCB's for one of these or get another Tandberg..... Regards Paulus.d

27th Jul 2009, 5:53 pm	#71
DOFFERY Retired Dormant Member Join Date: Aug 2004 Location: Blackpool, Lancashire, UK. Posts: 1,488	Re: Beloved Tandberg Series 15 Hi Paul, As you seem to have replaced almost the whole set & checked the voltages have you tried the quiescent current, measure across R133 no input , should be abut 16mv D C, adjust with R 129 Colin.

3rd Aug 2009, 9:06 pm	#72
Paulus.d Hexode Join Date: Mar 2008 Location: Margate, Kent, UK. Posts: 355	Re: Beloved Tandberg Series 15 Back now after sound engineering on high school musical in canterbury, uk. I have got a 0 to 30v power supply - will connect it to PCBS at the rectifier, I MUST rule out the transformer, it's AC volts test at lower than the 40v. So will connect tomorrow and try it. Paul

3rd Aug 2009, 10:04 pm	#73
af024 Octode Join Date: Jan 2003 Location: Ashby-de-la-Zouch (it's not by the sea) Posts: 1,255	Re: Beloved Tandberg Series 15 For what it's worth, mine produces exactly the same racket when the AMPLIFIER/PLAYBACK/RECORD switch is knocked. Perhaps you are getting the same? Regards, Andy __________________ Now where on earth did I remove that from?

4th Aug 2009, 10:54 am	#74
Paulus.d Hexode Join Date: Mar 2008 Location: Margate, Kent, UK. Posts: 355	Re: Beloved Tandberg Series 15 Your problem sounds like the switch. I've cleaned mine again and again to no change so I believed a cap was going down in the power supply. Does yours motorboat as described on this thread Its like a hum that builds up as you turn the volume up then it goes B-B-B-B with the lamps dimming If its like that too then we'll go back to the drawing board!!! Regards Paul Last edited by Brian R Pateman; 4th Aug 2009 at 5:19 pm. Reason: Redundant quote removed.

4th Aug 2009, 6:32 pm	#75
af024 Octode Join Date: Jan 2003 Location: Ashby-de-la-Zouch (it's not by the sea) Posts: 1,255	Re: Beloved Tandberg Series 15 I guess so. I do have to get the switch in precisely the right (wrong?) spot for it to do it. I don't relaly want to turn the wick up to see if the lamp dims at high volume, but I guess it would. I'm not saying that it definately the switch in your case, just that the symptoms seem very similar. Best of luck, Andy __________________ Now where on earth did I remove that from?

4th Aug 2009, 7:01 pm	#76
Paulus.d Hexode Join Date: Mar 2008 Location: Margate, Kent, UK. Posts: 355	Re: Beloved Tandberg Series 15 Tried an external power supply on the AMP - so I disconnected the AC side of the rectifier and soldered 2 wires to the DC power input at the point they join the 2 large caps. IT'S STILL GOT THE SAME PROBLEM!!!!! Only having a 0 to 30V supply I started at low volts and turned up. With the supply on full 32.6v the humming cuts in much earlier. Lower that voltage and it gets better at 16.6v any lower the sound stops completely. This note to Andy - if it's similar to yours then my switch must be ******** and I just can't spot it! I've now got to put the AC side back so I can test out some more theories, including the switch again. Perhaps I'll play with the contacts and see what happens... Stay tuned for the next exiciting episode!!! Paulus.d

4th Aug 2009, 7:56 pm	#77
af024 Octode Join Date: Jan 2003 Location: Ashby-de-la-Zouch (it's not by the sea) Posts: 1,255	Re: Beloved Tandberg Series 15 Keep chomping at the bit Paul, We are all eager to know what's going on here ... Regards, Andy __________________ Now where on earth did I remove that from?

4th Aug 2009, 8:48 pm	#78
Paulus.d Hexode Join Date: Mar 2008 Location: Margate, Kent, UK. Posts: 355	Re: Beloved Tandberg Series 15 thank you for having faith in me........ Also, as I have replaced caps already, I now know the caps I took out are OK - so I'll be using some of them to replace the caps I didn't swap!!!!! As already mentioned on the thread - if the lever is pushed into AMP and an input provided, the unit does not do the fault, if you push lever to record the monitor output does not do the fault - in both cases the MIC or RADIO input is fed directly to the AMP PCB bypassing the pre-amp board. therefore that PCB will take most of my attention, strangely thats the one with the AMP-PLAY-REC slide-switch! Regards PAul

5th Aug 2009, 8:26 pm	#79
The General Hexode Join Date: Apr 2007 Location: Milton Keynes, Buckinghamshire, UK. Posts: 329	Re: Beloved Tandberg Series 15 Now I've got one of these, the half track version. The things which are worth checking at this stage are the earths. There's a lot of gain in this machine (especially in playback) & Tandberg carefully seperated the low- & high-level parts of the circuit to avoid earth loops & feedback. If you look at the circuit, the power amp & regulator are grounded via the heatsink, whereas the low-level high gain bits are all grounded at one point via the body of the microphone socket. The impedance between these two points needs to be very low. So check that the microphone socket is firmly fixed to the chassis top plate with no corrosion, similarly the heatsink onto the main chassis, also check the chassis top plate is firmly bolted to the main part of the chassis. Worth checking to eliminate the possibility of poor grounds exacerbating your problem. Cheers, Mark.

13th Aug 2009, 6:07 pm	#80
af024 Octode Join Date: Jan 2003 Location: Ashby-de-la-Zouch (it's not by the sea) Posts: 1,255	Re: Beloved Tandberg Series 15 Does anyone have a close-up and sharp photo of the AMP/PB/REC switch (both sides of the contacts) that they could post? Let's have a look at how it looks, number of contact and where positioned and compare it with our own machines. Regards, Andy __________________ Now where on earth did I remove that from?