Uher Variocord 63 S

[DMcMahon]

I have solved the mystery of the little metal pin that must have come unsoldered when I removed the bad Microphone/Radio switch.

Looking at the switch end of the board (longways down) there is a vertical row of 7 pins the same size as the pin in question and above the top pin is a hole where the mystery pin has come out of, this hole is a small artwork pad connecting to one of the switch contacts (2/5 to be precise).

The top 4 fitted pins have a connector fitted where the top 2 pins are linked together and the bottom 2 pins are linked together. On the schematic the physical drawing of this connector is called "Bridging socket".

Looking at where the various pins physically connect to on the board and checking against the board artwork drawing, the pins are numbered 1- 8, with the mystery pin being # 5. Looking a the schematic could see 4 of the 8 connections (the 4 going to the bridging socket) but not the other 4 including pin # 5.

They seem to be for external connections but not identified as to what.

It looked like to me that the pins were for connecting to something external to the board with the bridging connector fitted when the external item is not fitted. Looking at the schematic for the stereo Variocord 263 it all became clear, because the 263 schematic identifies the pins on the schematic as "serve as connection when installing the automatic level control".

This rang a bell where sometime before I have read about an optional automatic recording level control and its schematics (mono and stereo) are shown in some (but not all) of the various Variocord Service manuals. So it is an optional board that is fitted somewhere and connected into the main board by wires connecting to the pins and the bridging socket would then be removed.

David

[DMcMahon]

Have now found a different version of the Variocord 63 schematic which like the 263 schematic also shows the "serve as connection when installing the automatic level control" information for the external connection pins.

[DMcMahon]

Hardwired the microphone DIN wiring (no longer switched by the Microphone/Radio push button switch).

Did microphone and Phono DIN line recordings & playback all good now. During this found that the phantom VU signal and noisy playback as per Post 13) was mainly due to a black wire that connects from 0V to the Play/Record switch metal cover, the wire was originally connected to the switch (0V connection) and was unsoldered when the switch was removed leaving the Play/Record switch metal cover floating wrt 0V.

[saxmaniac]

The Automatic level control is an extra board that plugs into the underside of the main board, if it's any help I can photograph the one I have

[DMcMahon]

Originally Posted by saxmaniac

The Automatic level control is an extra board that plugs into the underside of the main board, if it's any help I can photograph the one I have

Thank you, that certainly would be interesting to see for reference, I have never seen one.

David

[DMcMahon]

Originally Posted by DMcMahon

The other day after gluing the tape counter, refitted it but when I attempted to refit the drive belt it appeared to be too large/long. I say appears as virtually 100% sure it was the same belt that was removed and the counter was working then OK.

The fitting of the belt to the rear of the Take Up re table is impossible to see but I think I had the belt in the right pace. I tried to strip down the rear of the reel table to double check where the belt fits but after removing a few parts then hit a brick wall with one of those nearly impossible to remove tiny e-clips.

Had another go at refitting the tape counter drive belt, was sure it went around the middle section of the reel table hub but after struggling to fit, it does not drive the tape counter.

Impossible to see the belt around the table centre but assumed there must be a groove around it for the belt. Stripped off the back of the table to see better and then could see there is no groove but then could see that the belt groove is around the top part of the reel table.

But struggling to get the belt around the groove (and stay there) and also get the belt to go around the tape counter, a real test of patience !

[saxmaniac]

I don't know if you're trying to do this from underneath, but the silver control panel on top can be removed, 4 small screws and various control knobs and you can access stuff from there

[DMcMahon]

Yes have the all the silver front control panel parts off. In the end I had to remove the reel table to be able to put the drive belt around it then refit the table and thread the the belt back in, still was not easy.

Now the belt appears to be too tight and the counter will not rotate when table rotated (counter rotates easily with no belt). This belt is a square section one and I think new, the original was round, both belts look the same length.

The square section belt gets quite badly twisted along its length during stretching it and fitting it. Tried a few times removing and refitting but each time ends up twisted which I think effectively is making the belt tighter than it should be.

Next will try going back to the round belt.

David

[DMcMahon]

After fitting the round belt the counter now works fine but will swap the counter with another machine because the 63 S counter will not reset due to all 3 reset bars having broken off.

Later will also attempt repair of the damaged counter.

[Uncle Bulgaria]

This one has been putting you through the wringer! Well done on persevering, especially if your back's not feeling good. I imagine that casts a pall over most things. Uher seem to enjoy making belt-change a real challenge, but no doubt you're now becoming an expert!

[DMcMahon]

Fitted another counter and working fine. Retesting everything but now line recording has stopped working (Microphone recording is still OK).

Was using a different amp and cable so initially suspected them but after a few checks issue appears to be internal to the Uher ! so will have to go inside again.

[DMcMahon]

Traced problem to Phono to DIN cable wired incorrectly. Had recently made up several Phono to DIN recording cables with different values of attenuating resistors fitted in the cables.

Depending upon the signal strength of the external amplifier Phono outputs verses R2R DIN input sensitivity and Phono output impedance verses R2R input impedance, some amplifier Phono outputs overload some R2R DIN inputs, then requiring attenuating resistors in the signal lines to stop the overload.

The cable I was now using was marked up as the Phono signal going to pin 3 (via 220k in this case attenuating resistors) of the DIN connector, the Uher 63 S having the Phono input DIN signal wired to pin 3, but I found the cable had the signal wired to DIN pin 1. I had previously used this cable OK on another R2R where the DIN input just happened to be wired to pin 1.

So after correcting the cable wiring error, DIN line recording now works OK again. But a new problem now, on Playback of new or old recording am now getting loud regular clicks in addition to good playback sound, the clicks stop when tape is paused. Seems strange this has just started, so more fault finding required.

[DMcMahon]

Just started trying to trace the loud clicks. Typically with it opened up the regularity of the clicks has reduced.

Do not think power supplies are at fault, although there is some sign of reflection back.

> 30V p-p short duration spikes (only when tape is running in Playback mode) present before the volume control at least as far back as T4 collector.

Even though I have the component layout/artwork drawings it is not easy to correctly identify the relevant components then access them for monitoring, so will be a slow process.

[Ted Kendall]

Originally Posted by DMcMahon

Traced problem to Phono to DIN cable wired incorrectly. Had recently made up several Phono to DIN recording cables with different values of attenuating resistors fitted in the cables.

Depending upon the signal strength of the external amplifier Phono outputs verses R2R DIN input sensitivity and Phono output impedance verses R2R input impedance, some amplifier Phono outputs overload some R2R DIN inputs, then requiring attenuating resistors in the signal lines to stop the overload.

The cable I was now using was marked up as the Phono signal going to pin 3 (via 220k in this case attenuating resistors) of the DIN connector, the Uher 63 S having the Phono input DIN signal wired to pin 3, but I found the cable had the signal wired to DIN pin 1. I had previously used this cable OK on another R2R where the DIN input just happened to be wired to pin 1.

So after correcting the cable wiring error, DIN line recording now works OK again. But a new problem now, on Playback of new or old recording am now getting loud regular clicks in addition to good playback sound, the clicks stop when tape is paused. Seems strange this has just started, so more fault finding required.

Static discharge, maybe?

[DMcMahon]

Yes I did wonder about static. At times it sounds like actual sparking/arcing so last night I had a close look in the dark but nothing seen.

[DMcMahon]

Not yet able to home in on the source of the loud ticks. The spikey noise signal (smaller of course in the early stages of amplification) goes right back to the PB head signal but not sure if originating from there or just some reflection back into the head wiring

[DMcMahon]

From various tests believe that the electronics are largely exonerated.

From a few tests it is looking like it may be a tape problem, maybe static as Ted has suggested. Not easy to prove conclusively as even though when it occurs it is regular, sometime the ticks go away for 10 minutes so then difficult for example to be confident that another tape/spool does not give the same symptoms.

This morning was just about to have another look and now Play, FFD & RWD have all stopped working with no drive to either reel table. I think the machine knows I am preparing to sell it. Very frustrating but better that the faults occur now and be fixed rather than occur post selling it.

[DMcMahon]

Have found the cause, broken drive belt, hopefully it will be easier to fit replacement compared to the tape counter belt.

[Uncle Bulgaria]

I did read somewhere (perhaps here?) about a Walkman with static 'ticks', which turned out to be a nylon wheel picking up charge. A conductive 'whisker' brushing the offending wheel removed the charge so it couldn't build up.

[DMcMahon]

I have never experienced any static charging/discharging issues with tape up to now.

Replaced the broken drive belt which was very easy and tape transport control now working correctly again. I have a new Uher drive belt but have not yet located it (have far too many parts here, there and everywhere !), so have used a spare old Grundig belt.

The Grundig belt even though working well is slightly too long (a little loose) so will fit correct belt once I find it.