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Recapping a Tandberg TR-2080

Doug does nice work but he replaces everything and that isn't really necessary. Most go with the electrolytic capacitors and the relay as well as any devices known to be a problem, certain transistors get noisy, some varactors can be troublesome but these are done piecemeal not throwing everything out and that catches these devices, too.

It is your choice what to do. Maybe do some of the caps and see if you like doing that and give the unit a try and see if you hear a difference. Your unit, your time, your hobby to enjoy...you choice.
 
@dlucy , @Blue Shadow

Thanks for your comments. I will most probably go for much lighter path than Dlucy took. That is mainly because I lack expertise, skills and tools.
It is interesting to see how it all goes and how this develops. Unless it ends up in total disaster I might drop a few notes on separate thread as you suggested.
 
Looking forward to the new thread.

One caveat: there are at least two variants of the 2075 MkII. The early ones are closer to the late production 2075 electrically-speaking, and the later ones virtually identical to the 2080 as Doug mentioned. The later ones are covered by the combined 2075 MkII/2080 service manual (not the greatest scan, but it's free): http://sportsbil.com/tandberg/tr-2075mkii-2080-sm.pdf

and the earlier version schematic is here: http://sportsbil.com/tandberg/tr-2075mkii-s.pdf

Given your receiver is essentially working, along with my normal bias for keeping things original when possible, a minimal approach seems suitable.

I'd replace C610 (radial 1000uF/63V, can use a Vishay or Nichicon TVX-series cap here) for sure.

If it's an earlier version (check the value marking of the volume control pot vs. the schematics to determine this; they should be 25K or 50K depending on the version), all four of the vertically-mounted Frako-branded gold caps on the power amp board have to go. Two of those cause excess DC offset, and the other two may as well be done at the same time as they're all known to tend towards shorting as they age. You can replace all of those with same value parts, as a new radial cap can be had with the same pin spacing as those vertically mounted Frako parts. At the most you may have to nudge a couple of resistors slightly sideways to accommodate the new caps.

After that I'd check it for DC offset and distortion/noise, and let the outcome of those measurements drive the larger scale part replacement decision.

John
 
@jdurbin1
Thank you very much for your valuable input.

I was aware of Njord Noatun's database and schematics to be found there. Indeed some of the scans could be better but those are still better than none at all. Incase you are willing to hand a copy of those hires scans you have you can drop them here:

https://1drv.ms/f/s!AvsIE7NjYFEDmOg3i1cNUkA8ZX5DFw

I checked the volume control pot and it seems to be 25K so which of the versions this one actually is?

Thanks again! This is going to be my first project of this magnitude and I will see if anything is there to be reported other than a great failure.;)
 
Tanberg... great euro. brand name following.
There are no failures on AK! Lack of ability can always be overcome!
 
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25K is the earlier version, note R701/702 value in the schematic vs. the 50K value for same pot shown in the MkII/2080 combined manual. It'll also probably be a pot with cast metal housing, not the more open type used later - but that's just my recollection.

I quit posting my own scans to Njord's site - for the most part, there are a few in there - because I got tired of asswipes copying them for their Tandberg manual compilation CD's to sell on eBay. Not Njord's fault of course, his motives for making that and other brand archives available for free are entirely pure and supportive of the actual gear owners, techs and collectors alike, but I decided not to help put money in those pirates' pockets any more.

John
 
Thanks @jdurbin1
The housing really is as you described above.

Perfectly understand your decisions (would do the same if that is the case, what a shame) and after all we have identified the version to be the earlier one so I believe I will manage perfectly with that scan as its quality is much better than the one about the later model. Thanks for your input.

I will open a new thread about mk II speaker terminal replacement and recapping during the weekend.
 
Saw it, looking forward to following your progress.

By the way, you can - and should - use the full TR 2075 service manual for reference as well; although the combined one for later version has a lot of overlap, you may find in some areas like FM board or preamp that your example is closer to the late production 2075. Amp board may be the same as well.

John
 
dlucy said:
Looking around AK, it sounds like some folks have replaced the 2SC1583 with a pair of 2SC2240's, KSC1845's, BC639-16's, or BC550's.

The 2SC2240's are no longer made, the KSC1845's handle too little current (50 mA instead of 100mA), and the BC639-16's are backordered.

(Note: a pair of KSC1845's were used in this thread)

Looking at the Low Noise Transistor list, it looks like SS9014 or BC550 would be the best available choice, so I'm going with a pair of BC550 for each 2SC1583. I'll have to twist the leads a bit....
Click to expand...
You can find Chinese copies of the 2SC2240 on Ebay.
You might want to consider PN2484, 2N6428, 2N5961...They would give you some safety margin.
NOS 2SC1583 from US sellers also available on Ebay
HTH

Soundork
 
Soundork said:
You can find Chinese copies of the 2SC2240 on Ebay.
Click to expand...

it has been my experience that I can find devices for sale on eBay from China which have been labeled as a particular device, but whose actual performance is less than the specs quoted for that device from the original manufacturer. Hence, not reliably the advertised device.

the original 2SC2240 devices have very low noise figures and high gain. Personally, I have no faith in ebay-bought China-sourced devices meeting these specs.

Soundork said:
You might want to consider PN2484, 2N6428, 2N5961
Click to expand...

When you recommend these replacements, are you including the noise figure as one of the specs that these match or exceed when compared to the 2SC2240 and KSC1845?

Answering my own question after taking the time to look it up myself... which I should have done in the first place: yes, the devices @Soundork is recommending are low noise. They aren’t quite as low noise as very low noise devices (see link in my signature and below), but they definitely qualify as low noise.

http://www.audiokarma.org/forums/index.php?threads/low-noise-small-signal-transistors.815432/
 
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Brilliant thread, @dlucy. I have a 2075Mk1 that I'm leaving alone for now (working), but have recapped (mostly) a TR-1055 and am now diagnosing why the pre has no output and only one channel of the power amp is working (possibly rectifier bridge). The Tandbergs are really beautiful but they are a puzzle to disassemble/reassemble! I dread the day I have to put the 1055 back together.
 
dlucy said:
it has been my experience that I can find devices for sale on eBay from China which have been labeled as a particular device, but whose actual performance is less than the specs quoted for that device from the original manufacturer. Hence, not reliably the advertised device.

the original 2SC2240 devices have very low noise figures and high gain. Personally, I have no faith in ebay-bought China-sourced devices meeting these specs.



When you recommend these replacements, are you including the noise figure as one of the specs that these match or exceed when compared to the 2SC2240 and KSC1845?

Answering my own question after taking the time to look it up myself... which I should have done in the first place: yes, the devices @Soundork is recommending are low noise. They aren’t quite as low noise as very low noise devices (see link in my signature and below), but they definitely qualify as low noise.

http://www.audiokarma.org/forums/index.php?threads/low-noise-small-signal-transistors.815432/
Click to expand...
Note that the devices I recommended are also high DC-gain devices. The KSC1845 is not. I have purchased two batches in the past and the components failed short of the advertised typical value. I measured gain in the 345-387 range.
Best
Soundork
 
Soundork said:
Note that the devices I recommended are also high DC-gain devices. The KSC1845 is not. I have purchased two batches in the past and the components failed short of the advertised typical value. I measured gain in the 345-387 range.
Click to expand...

Yep. You'd have to choose either not-as-high-gain-but-much-lower-noise or high-gain-but-not-as-low-noise. I'll get the devices you listed added to my list... and think about making a decision-tree thingie.
 
ekholve said:
@dlucy , @Blue Shadow

Thanks for your comments. I will most probably go for much lighter path than Dlucy took. That is mainly because I lack expertise, skills and tools.
It is interesting to see how it all goes and how this develops. Unless it ends up in total disaster I might drop a few notes on separate thread as you suggested.
Click to expand...

Do it. Even if you think that this project is over your head. There are number of smart people such as, Blue Shadow and dlucy that would help you succeed.

If I may suggest:

If your unit is malfunctioning, fix the problem first. Then decide how far to go with part replacement.

I wouldnt waste money on "the best of the best" or "exotic" devices. Just ensure that it is a low noise device purchased from reputable dealer. I doubt that you would hear any difference between any of them once in circuit, despite spec claims.

You will see significant improvement once you replace the electrolytic capacitors. Same as for the active devices: No need for "exotics".

Take your time. You will be significantly faster while tackling your next project...:)

Best

Soundork
 
Soundork said:
You can find Chinese copies of the 2SC2240 on Ebay.
You might want to consider PN2484, 2N6428, 2N5961...They would give you some safety margin.
NOS 2SC1583 from US sellers also available on Ebay
HTH
Soundork
Click to expand...

Nice suggestions for low noise transistors here. I did not know these. Somewhere in this forum it was also suggested to use SMD parts to replace differential pairs because they tend to dissipate low power in this application. An SMD part with hfe and noise figures comparable to the 2sc2240BL but limited to Ic 100mA and 100mW power handling is the Toshiba 2SC4117BL currently in production and available from trusted suppliers. It is harder -but possible- to glue a pair of these parts. It is worth considering it. There is also a PNP complement to this part (the 2sa1163BL).
 
Personally, due to the high signal levels/low impedance circuit, those noise figures will not be important, at all, I think.

Nor does max collector current specification due to the low current.

But as AVERAGE power handling of each input transistor is already 50 Volts times 1.5 milliamps (75mW) each transistor, I do not think using a 100mW max SMD device having max 125 degrees celsius junction temperature is a good idea in this case.
According the derating graph the transistor is at its absolute limits at 50 degrees celcius when dissipating 75mW. It will reach that temperature by heating itself.
 
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Thanks @dlucy for this thread. I came into possession of a TR-2055 a while ago. After warm up it would fall off significantly in level on the left channel. Sometimes the channel would be low and distorted on power up but playing with the volume knob would correct it...for a while. I used DeoxIT on all pots and switches but continued to have the problem. A trip to an old radio service store corrected my stuck tuner but they couldn't fix the level issue. After two trips I gave up. Would a recap be the fix?
I would not have attempted this a while ago but having just refurbished a Thorens TD-124 I'm now up for it.

Thanks in advance to any with suggestions.
 
Playing with the volume wouldn't resolve a failing capacitor. My first guess is oxidized contacts on one channel of the protection relay but there are other possibilities including cracked solder joints or failing switch(es) or pot(s) - sometimes spraying deox from outside won't fully resolve really badly oxidized contacts inside these components.

If you can consistently make sound go back to normal on that channel by just raising the volume, 99% it's the relay. Sliding a clean white piece of card stock soaked in contact cleaner between the contacts usually fixes that, if the oxidation is bad enough you may have to look into a replacement relay.

John
 
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