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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 31st Jul 2019, 2:20 pm   #1
jascha
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Default Tandberg Series 15. No sound on playback position. help please

Hi everyone,

I recently was given a Tandbery S15 2 Track as a gift to add to my collection and it needed some TLC as it was all gummed up, but after some lubrication it got going.

I decided to do a recap job on it as it has the old Frako and Rifa electrolytics however I seem to have run into trouble as after replacing 3 caps I lost the playback sound. The machine was playing fine before the recap job has started. To those that know the insides of the machine, they are aware that the slider switch mechanism (Rec-Playback-Amp) needs to be removed from one end in order for the upper board (pre-amp) to come out. This is the only board that i had started work on and believe has an issue now.

I decided to put back the 3 old caps anyway but still i get no sound from the playback position. In the Amplifier mode, I can playback a source I input via the radio input jack.

I have a suspicion that something is not quite right with the slider switch mentioned above and although i have cleaned it, i cannot get any sound from tape. Clearly the head is fine and I guess everything else should be fine too since it played before i started restoration. I would like to know if these switches are really a problem and if by chance there might be some copper tracks that could have been compromised during removal/cleaning of the slider switch contacts. The level of hiss between the amp and playback positions are quite significant. unfortunately there seems to be no image of the small slider switch contacts on the service manual for me to compare with.

Any thoughts please would be most gratefully received as i would love to get it going again.

Thanks
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Old 31st Jul 2019, 2:27 pm   #2
Paulus.d
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Default Re: Tandberg Series 15. No sound on playback position. help please

These Tandberg recorders and their slide switches are trouble …. I have two of these ..both have have trouble with those....
check the little top hats on the contacts have not fallen out … mine do

Regards Paul
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Old 31st Jul 2019, 4:08 pm   #3
jascha
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Default Re: Tandberg Series 15. No sound on playback position. help please

I believe they're intact, all 5 of them. (There should be just 5 contacts right?). If I have time I try to open up the machine and take a photo of both sides of the slide switch.

I don't think it should be an issue with the hats not being in place as otherwise I would not have any output either with the switch in the AMP position surely (?).
It's definitely an issue with the upper board as i have not touched the lower Power Amp board and there is output from the Radio input jack.

Could it be another component? My instinct says no as when the slider switch is in the middle position the background noise is close to minimal, compared to when it's in the AMP position (hissy). The playback head measures around 76 ohms for both tracks. I think that's all fine.

Cheers
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Old 31st Jul 2019, 5:07 pm   #4
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Default Re: Tandberg Series 15. No sound on playback position. help please

Here are 2 images of both sides of the switch. I have cleaned it thoroughly in the meantime and will check for any broken connections between head cables and pre amp board. I have noticed that hiss levels are higher on the amplifier mode than playback mode, however there is still some background noise in playback mode.

Thanks again
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Old 31st Jul 2019, 8:07 pm   #5
Paulus.d
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Default Re: Tandberg Series 15. No sound on playback position. help please

That switch looks very good .... wish mine was that clean!!
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Old 1st Aug 2019, 8:04 am   #6
ricard
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Default Re: Tandberg Series 15. No sound on playback position. help please

I agree, the switch looks good, besides, I've never had a switch give up the ghost entirely, rather, it tends to be very sensitive to the position of the slider when not clean, but it's usually always possible to find some position of the slider that results in sound, often with an inordinate amount of crackling in the speaker while the switch is being moved.

I would think there is some component lead that has broken while you were handling the board, e.g. a marginal solder joint, or a component lead that was damaged in production but has just survived over the years.

Another thing to check, since it is only in the playback position that there are problems, have you checked the solder joints between the switch PCB and amplifier PCB? The switch PCB is just stuck in an oblong hole and held on with the solder joints to the amp PCB, not the best of designs mechanically, but it usually works well enough.

And another, more obvious thing: have you verified the continuity in the lead from the head to the point where it arrives on the PCB? In case it's one of the crimped connectors that has failed. Also, I seem to recall there's basically one long connector that connects the rest of the machine to the PCB, but also a couple of smaller spade connectors which are easily overlooked.
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Old 17th Aug 2019, 9:07 pm   #7
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Default Re: Tandberg Series 15. No sound on playback position. help please

Hi everyone,

Thanks for all your help and only today I could work on my machine and am happy to report that the fault was no other than my silly mistake! The reason I lost the sound was due to an error while soldering some fresh caps on the pre-amp board. I had only changed just 3 electrolytics when it happened and due to the boards being so delicate and had not used a solder wick to remove components (just used a desoldering pump), a few of the solder pads had lifted and therefore I had to jumper across some connections. As at the time of doing this job I was not fully focused (family visiting etc) I jumpered to the wrong point on the board which resulted in the two negatives of C202 & C201 coming into direct contact and therefore shorting the output of the signal from the head practically straight to ground!

I started scoping the signal and I was not getting much further than the playback head!
I was pleased to realize my error...it can happen especially when tracks are so close to each other and of course lack of focus.

It's working flawlessly now . Now I would like to find a perspex cover for it and hopefully one day one will turn up.

Thanks again to everyone who helped me.
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Old 18th Aug 2019, 10:25 pm   #8
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Default Re: Tandberg Series 15. No sound on playback position. help please

It's strange how the real fault always appears to be something else than originally envisaged! Good to hear it's working fine now and that no other damage was caused!

As I side note, I don't think I've ever had to replace a component in a Tandberg 14 or 15 (not that I've seen that many, but it's certainly more than 5 although perhaps not more than 10 at this stage). Rifa paper caps are known for their shoddy quality in terms of electric leakage and the way the package cracks with age, but I've not heard any such generic rumors about their electrolytics. Of course, electrolytics do age, which is one reason some people recommend replacing them, on the other hand, on a machine that's not really intended as a HiFi device, the degradation in performance (compared to other parameters) is under normal conditions rather minimal. And as your story does make clear, recapping is not without risks.
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Old 18th Aug 2019, 10:34 pm   #9
jascha
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Default Re: Tandberg Series 15. No sound on playback position. help please

As I said, the issue was caused by working whilst not having the freedom of time and had limited time at home during my holidays too. Yes it's true that the machine is working well (apart from some noisy mechanical issue during playback), however I feel that these caps by now would be on their way out and start drying up and that's why I felt that they should be replaced. It's not an emergency however but the lesson learnt here is that one should perhaps use a wick rather than a pump to desolder components. With such boards that have a certain age, using a wick is I guess a more gentle way to desolder components.

I have seen similar caps on Revoxes and Studers and they tends to be troublesome if not replaced in time, so that's why I feel that they should be replaced in the Tandberg...a measure of precaution.
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Old 19th Aug 2019, 9:52 am   #10
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Default Re: Tandberg Series 15. No sound on playback position. help please

My experience with vintage recorders (1960s and 1950s) has been that electrolytics rarely fail regardless of age, although I rarely measure performance on older machines so I wouldn't know if they were slowly loosing capacitance for instance.
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Old 19th Aug 2019, 9:03 pm   #11
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Default Re: Tandberg Series 15. No sound on playback position. help please

Quote:
Originally Posted by ricard View Post
My experience with vintage recorders (1960s and 1950s) has been that electrolytics rarely fail regardless of age, although I rarely measure performance on older machines so I wouldn't know if they were slowly loosing capacitance for instance.
Frako electrolytics do.
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