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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 6th Dec 2016, 10:02 pm   #81
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Default Re: Tandberg 64x after changing capacitors

The readings on the other valves are a bit off, but I think it's worth trying a functional check.
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Old 7th Dec 2016, 6:42 pm   #82
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Default Re: Tandberg 64x after changing capacitors

Thank you so much Graham and Lawrence for all your input and help on this.

I have done a test. Both channels are getting signals, but very very low. I have connected my iPhon through a minijack stereo to RCA and inserted in to the input low volume rca's...

Could this be becuse i am connecting a low level output device to the recorder? The magic eyes are responding fully with high amount of volume however the sound is very very low barely can hear it...

Maybe some other components are gone on the amp section....?
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Old 7th Dec 2016, 7:20 pm   #83
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Default Re: Tandberg 64x after changing capacitors

When you say low do you mean you've tried recording from a source but when you play it back the sound is low?

From what you say it looks like the recording signal might be reaching the recording heads because the take off point for the magic eye indicator is more or less at the same point that the record heads are connected to, there are a couple of switch contacts at that position that feed the heads, I assume that all contacts are clean and that the record, playback, bias heads are absolutely clean and not badly worn.

I have not studied the circuit fully yet.

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Old 7th Dec 2016, 8:18 pm   #84
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Default Re: Tandberg 64x after changing capacitors

Hi Lawrence,

No, i have not recorded anything on them, just feeding with the signal, and connected my headphones to the outputs....when i press the record buttons 1+2 down, the signal is still the same, very low...or is that maybe normal and I only need to hear proper volume on playback? I have not tested any playbacks yet, as i thought i should be able to hear a good amount of volume first, but i dont know much this machine too..

The heads on this machine surprisingly in very very good condition. I have also cleaned with 93 percent of medical alcohol...

Thank you
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Old 7th Dec 2016, 8:57 pm   #85
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Default Re: Tandberg 64x after changing capacitors

If you haven't already done so I would suggest cleaning all switch contacts with Servisol or its Hungarian equivalent. This along with cleaning the heads is one of the first things that should be done with a reel to reel tape recorder before embarking on changing any components.

If you have a pre-recorded tape try playing that back. It has the advantage of testing just the playback section.
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Old 7th Dec 2016, 9:06 pm   #86
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Default Re: Tandberg 64x after changing capacitors

Quote:
Originally Posted by Levente View Post
No, i have not recorded anything on them, just feeding with the signal, and connected my headphones to the outputs....when i press the record buttons 1+2 down, the signal is still the same, very low...or is that maybe normal and I only need to hear proper volume on playback? I have not tested any playbacks yet, as i thought i should be able to hear a good amount of volume first, but i dont know much this machine too..
I haven't worked out the switching yet but so far as I can make out the output from the record pre amplifiers V1 & V2 (apart from feeding the record amplifiers) are connected to point 5 (left hand channel) and point 6 (right hand channel) on the record amp board and from there via the switches and the output level controls R18 & R19 to the inputs of the left hand channel and right hand channel cathode followers the output from the followers feed the output sockets.

If the output is low on both channels then that would suggest a problem common to both, not sure what yet, I'll have another look and a think as and when.

Also wait to see what Graham thinks.

EDIT: Post crossed with Graham's

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Old 7th Dec 2016, 9:09 pm   #87
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Default Re: Tandberg 64x after changing capacitors

Thanks Graham, will do definitely. I have tested the recorder just now. It seems that the channel R (as on the indicator light) is very low in volume, the channel 1 and 2 is definitely not equivalent in terms of volume. I have recorded a test, tried to find a clean song of one of my fav. Floyd...well...listening back the recording it does what the indicator lights are telling me. Left channel has volume but very dark, kinda muffled sound with no top end at all...R channel is out.

Is this something to do that the ecc 81s has very different voltages?

I feel that we are nearly there saving to this beauty with your help guys...or am i too optimistic?
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Old 7th Dec 2016, 9:14 pm   #88
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Default Re: Tandberg 64x after changing capacitors

Thanks Lawrence...its getting a bit complicated for me.. the sound is not too bad if just play the music through the unit but if i hit the record, there is hen the problem comes...not sure is the best thing also to run music from an ipad straight in to this machine without proper amplifiction..i guess the slight distorsion comes from there too...

but the playback from the tape sounds pretty bad...L channel is dark low volume...R channel is out...the playback is hat i have just recorded and not a pre recorded tape

Last edited by Levente; 7th Dec 2016 at 9:23 pm.
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Old 7th Dec 2016, 9:23 pm   #89
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Default Re: Tandberg 64x after changing capacitors

Quote:
Originally Posted by Levente View Post
Is this something to do that the ECC81's has very different voltages?
Before you think about changing valves check the value of the resistors, they're much more likely to be faulty.
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Old 7th Dec 2016, 9:27 pm   #90
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Default Re: Tandberg 64x after changing capacitors

I'm a bit rusty in my old age but 40 years ago I used to service tape decks and video decks for Sony, 90% of record/playback problems were down to dirt on the heads, worn heads, defective tape path or dirty switch contacts, the former and the latter being the most common, I'm not saying that is the problem in this instance but the heads if not badly worn have to be spotlessly clean, you need very good eyesight or a magnify glass to check properly, muffled sound was a typical symptom of dirt on the heads, nothing abrasive should be used to clean tape heads, not even a plastic card.

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Old 7th Dec 2016, 9:42 pm   #91
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Default Re: Tandberg 64x after changing capacitors

Thanks guys again...will double check the heads, head alignment and will check all the resistors just in case...

For the test I have just done I have used a brand new tape. And in terms of the heads, i will go and clean again very gently...visually they looked very clean.

Graham, Lawrence, thank you. Without you guys I would still stuck with no progress scratching my head what to do...good night guys, will update later on

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Old 8th Dec 2016, 7:40 am   #92
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Default Re: Tandberg 64x after changing capacitors

Hi Lawrence, just a quick note as I think it is important to mention before I do anything else with regards you previous post of the R18 & R19 and the oscillator board. The PCB printout I have followed includes this oscillator board on Fig 58. However, in my machine there is different. There is a separate board which I believe could be the oscillator board but without the ecc82s. I have noticed that the other day too that these printouts are for the Tandberg 62-64 and mine is 64X.....or maybe I am looking at the wrong place...

The other thing is that I have not changed two of the electrolyt caps, the C110 and the C213, as these were somehow different to the others. These are like 4 legs caps with + in the middle, old Siemens caps.

Would you advise to change these caps too, or shall I just leave everything as it is for now until the heads recleaned and the resistors checked...

I am really confused on on the oscillator board

Last edited by Levente; 8th Dec 2016 at 7:52 am.
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Old 8th Dec 2016, 10:05 am   #93
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Default Re: Tandberg 64x after changing capacitors

I would leave those two capacitors for the moment.

The only manual I have a copy of is for the Tandberg Model 64 & Model 62:

http://www.sportsbil.com/tandberg/62-64-sm.pdf

The oscillator circuit is on a separate board and contains no valves as it is transistorized.

In post#86 I made no mention of the oscillator circuit.

To help to understand what you've been saying earlier lets try and one function at a time.

1) As Graham as already suggested, play back a known good recording and describe any symptoms.

2) Make a recording and note if you can hear an output whilst that recording is in progress with the output level control turned up, if you can hear an output is it good on both channels ?

3) Playback the recording just made and describe any symptoms.

The above assumes that the heads are absolutely clean.

Respond with answers to questions 1), 2) & 3) Eg:

1) (answer)
2) (ditto)
3) (ditto)

It helps make communication easier.

Should be able to crack this.

This post might cross.

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Old 8th Dec 2016, 6:24 pm   #94
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Default Re: Tandberg 64x after changing capacitors

Hi Lawrence,

Thank you.

Answers:
1) At the moment I don't have a pre recorded tape, i will get one asap.

2) Made a recording. While I was doing it, output not so good. Left channel muffled dark sounded, no eq, no high freq. R channel nearly out, not hear-able and all this is when I have switched to A+B channels on the recorder, so I am monitoring on the spot whats being recorded on A+B.

3) Playing back the tape sounds exactly as above.

The unit sounds quiet OK when I feed music from an external source, the only issue is that the channels are not equally balanced. L channel much louder and has more gain then the R channel. This is not on the A+B monitoring mode as the tape is not being recorded or played.

I hope i am not confusing things here

Levente
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Old 8th Dec 2016, 8:02 pm   #95
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Default Re: Tandberg 64x after changing capacitors

I'm wondering if there could be some problem with the handling of the machine. It doesn't explain any discrepency between the channels of course. Sorry for the description below if all this is obvious.

When the rotary switch underneath the playback level controls is in the NORM position, you cannot monitor the signal off the tape. In this mode, when the PLAYBACK buttons are up, you'll monitor the signal from the recording amplifier. With the PLAYBACK buttons down, the output is silent if I remember correctly.

With the rotary switch in the A-B TEST position, you can monitor the signal off the tape during record, when the PLAYBACK buttons are depressed. This is termed 'B-test'. When the PLAYBACK buttons are up, you monitor the signal from the recording amplifier as in NORM mode. This is termed 'A-test'. The term 'A-B test' refers to testing the sound (i.e. listning) before it's recorded on tape vs. after, i.e. when played back.

I don't know why there is a NORM mode, since it doesn't seem to offer anything compared to A-B TEST mode, except the inability to monitor off tape. Later Tandbergs do not have that switch, and are essentially always in A-B TEST mode, with the PLAYBACK buttons selecting whether the output is fed from the recording amplifier, or taken from the tape playback.

Another quirk is that when pressing only one of the PLAYBACK buttons, the corresponding signal is sent to both output channels. This is for listening to a tape with two separate mono recordings on tracks I and II, but still getting a signal on both the channel I and II output connectors. In practice, it saves you from having to press the MONO button on the attached amplifier when only listning to a single track.

Back to item 2) in the previous post. I can't really make out if the OP is performing an A-test (PLAYBACK buttons up, listning to the record amplifier) or B-test (PLAYBACK buttons down, listning to the tape). If it indeed is the former case, there's something seriously wrong in the amplifier circuitry if the sound is muffled. If it is the latter case, i.e. off tape, then the problem could well be dirty heads, or alternatively severe head position misalignment or other tape path problem, but it could also be an amplifier problem. With the 6X there's also the additional possibility of the bias head not being positioned correctly, which could be a mechanical problem or misalignment, but normally, a recording made with the bias level way too low will be not only quiet but also distorted, and with too much high frequency content.

Last edited by ricard; 8th Dec 2016 at 8:07 pm.
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Old 8th Dec 2016, 8:19 pm   #96
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Default Re: Tandberg 64x after changing capacitors

Well...that saved me writing a pile, it's more or less the conclusion I came to after looking at the manual, it's possible that there's an electronic problem and a head(s) problem if getting poor results for the A & B tests, assuming that the input levels for both channels are equal

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Old 8th Dec 2016, 9:10 pm   #97
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Default Re: Tandberg 64x after changing capacitors

Thanks Ricard, Lawrence.

Okay.

switched the unit to A+B

I am feeding music to the unit when the playback buttons are depressed--> I am getting an OK sound with a less signal gain on the R channel.

When the recording buttons are pressed down (tape not moving as it is in the break position)-------> I am getting an OK sound with the less signal on the R channel. (same as above) and can be seen on the magic eyes too but according to the gain setting this should be equal.

When I release the break, so I am recording, and because it is on A+B, I am listening on the spot as soon as the tape starts moving with the playback buttons also pressed down.... This is where the problem is, this is where the muffled sound is, this is where the R channel is very weak..... and the same when I play back what just been recorded.

So if I understand you guys and Ricard correctly, the problem is at the B TEST...when i am recording with the record buttons and the playback buttons are engaged....so this could either be a dirty head or some amplification problem, or heads misalignment.

The readings of the tubes ecc81s can be a source of the quieter R channel ?

One of them had nearly double voltages on the pin 1...?

I will clean the heads too again and will get a prerecorded tape to see what is happening with that one.

Really thankful for you guys to help me on this. Please understand that I am not an expert, not a technician and certainly not familiar with tube based gear however I love vintage gears, the sound of the tube they are producing.

Audiophysics were and is far away from me however I have learned a lot and something new every day.

Thanks for your patience!

Levente

Last edited by Levente; 8th Dec 2016 at 9:18 pm.
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Old 8th Dec 2016, 9:34 pm   #98
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Default Re: Tandberg 64x after changing capacitors

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The readings of the tubes ECC81's can be a source of the quieter R channel ?

One of them had nearly double voltages on the pin 1...?
According to the service sheet the two ECC81's have different voltages on their pins, with the exception of course of their heater pins. I must confess that I have not studied the circuit in sufficient detail to see why this should be.

If you are really concerned about it, swop over the valves and see whether the fault moves with the valve.

As I've said before though, resistors and capacitors are far more likely to be faulty than valves. Anode resistors have a habit of going high in value.
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Old 8th Dec 2016, 9:45 pm   #99
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Default Re: Tandberg 64x after changing capacitors

"I will clean the heads too again and will get a prerecorded tape to see what is happening with that one"

Yes, that would be a good move now, it only takes a small amount of dirt on the heads to mess things up, the dirt is mainly oxide that comes off the tape, the heads have a very small gap in the magnetic core, in effect it's the magnetic information (which varies according to the electrical signal) across that gap which is recorded on to the tape and read off the tape when the tape is played back, anything that impedes the transfer of that magnetic information can cause bad signal loss especially on the higher frequencies (very basic explanation)

EDIT: Post crossed again.

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Old 9th Dec 2016, 10:35 pm   #100
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Default Re: Tandberg 64x after changing capacitors

Quote:
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Quote:
Originally Posted by Levente View Post
The readings of the tubes ECC81's can be a source of the quieter R channel ?

One of them had nearly double voltages on the pin 1...?
According to the service sheet the two ECC81's have different voltages on their pins, with the exception of course of their heater pins. I must confess that I have not studied the circuit in sufficient detail to see why this should be.

If you are really concerned about it, swop over the valves and see whether the fault moves with the valve.

As I've said before though, resistors and capacitors are far more likely to be faulty than valves. Anode resistors have a habit of going high in value.
I've just had another look at the circuit diagram and I can see no reason why the voltage readings on the ECC81's should differ between the two valves., so perhaps there's an error in the document?

So maybe, as suggested, swopping the valves and checking the resistors might not be a bad idea.

Bear in mind though that these valves are only used during recording.
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