Uher Variocord 63 S

[DMcMahon]

Tonight have been having a look at my latest acquisition, a Uher Variocord 63 S, a 2 track mono solid state 7" R2R. It cost less than £5 so my expectations were not high.

Still fairly early days, but it is looking promising. Overall quite reasonable condition for its age, internally like most Uhers I have worked on, surprisingly clean internally (compared to many other different makes).

Checked the mains voltage selection switch, it was correctly set at 200 - 240 volts, most of my other Uhers have a 240 volts setting.

Replaced the 2 core continental mains cable (unit came from Germany) and 2 pin mains plug with 3 core + 3 pin mains plug. Replaced corroded internal 20mm 0.3A mains fuse with new 315mA fuse.

Did a few safety checks and switched on, but nothing happened. Found that this model has an EOT (End Of Tape) switch mounted on the LHS of the tape path which connects one side of the mains (I wired it as Live) to the internal mains fuse. This EOT switch is not fitted on my various other Uher models.

Then fitted tape and it powered up OK. Tape transport works well and Play works on all 3 speeds. There is a problem with Pause, the pinch roller is not fully coming away from the capstan shaft and even if manually pulled away from the shaft, the Take Up reel table still have enough drive/tension to keep rotating at erratic speeds, so will need to look at that further later.

Initially playback sound was very weak/quiet but after a few minutes of checking various, it came good with plenty of clear volume.

Sometimes when switching on/off get nasty clicks in the speakers (even though mono still has 2 internal speakers). So later will have a look at the power supply and reservoir capacitors etc.

[DMcMahon]

Investigating Pause not working issue found 4 separate issues, although first two when fixed did not help the pause issue.

The pinch roller arm assembly was gummed up and stiff on its pivot shaft. stripped cleaned and re-lubed. A small brass tape tension guide assembly was gummed up and not rotating, good after strip, clean and lube.

The 2 issues actually stopping pause from working was 1. The Supply Reel Table brake was not holding/braking the Supply Reel Table. Increasing spring tension on its tension spring did not help. After stripping and cleaning the rubber brake assembly and cleaning the side edge of the reel table, the brake is working very well now.

2. This nearly got pause working but the Take Up reel table clutch torque was too strong and its drive could overcome the Take Up reel table brake, so had to bend/tweak Rod R (as per SM procedure) to actuate the take up sensing lever more to the left to reduce the torque.

Investigated the horrible loud clicks when unit switched on/off (Note to change tape speed you have to switch through intermediate off positions). On scope could see HF noise spikes all over the electronics, up to at least 60 volts p-p when switching on/off, worse I would say when switching off.

After various diagnostics came to conclusion that nothing obviously bad in the electronics and thought that the noise spikes were originating from the 2 pole on/off mains switch contacts arcing and being radiated out as RFI/EMI.

Fitted a 0.1uF 275VAC X2 Safety Suppression capacitor across the output side of the mains switch and this has completely stopped the audible noise with some very minor disturbances still seen on the scope. Better result than I hoped.

[David001]

Lovely. I was after one of them, to go with my 4000 ones. Hope you get it going!

[DMcMahon]

Microphone and DIN line recording not working at all. Microphone/Radio push button input selector switch not staying down/latching in the Microphone down position.

[DMcMahon]

Found that the mechanical actuation for the Radio/Microphone selection push button switch is broken. Not sure if plastic piece is missing or just broken off. Possibly may be able to glue the remains of the plastic piece direct to the switch shaft, but will not be easy as difficult location to access and a strong spring fits first and that will be pushing strongly against the glued joint. Plus also I cannot see how it latches in the down (Microphone) position.

Also the push stroke distance of the switch shaft has to be correct, as if it goes in too far the switch contacts open, so after gluing repair may also have to somehow adjust the stroke distance.

First will manually set the switch positions (determined my meter measurements) and see if I can get recording to work in both Radio and Microphone settings.

Think this is going to be a serious challenge !

[DMcMahon]

With Radio/Micro push button switch manually set, both in Radio and micro position checked recording, all worked well.

Determined that the latching on/of action of the switch is purely due to the switch itself and by holding a little metal piece of the switch in the right position and manually holding the spring and the plastic plunger it felt like it may still latch if I can get it glued together.

Had 2 attempts at gluing (had to tie back the spring) but both attempts failed to hold for long. Will have one more attempt, if this fails will look into replacing the 4PDT switch assembly, although struggling to see compatible part with same pin spacing etc (did see one in USA but high price).

[DMcMahon]

Third attempt at gluing failed because could not keep the strong spring back enough to not disturb the glued joint. Removed the switch, which was extremely difficult, the soldered connections were directly under the switch body so difficult to get to and the switch was really tight in the PCB holes. More with force than finesse got the switch out, several of the PCB artwork pads/tracks will need repairing when switch is refitted.

With switch out it will be a little easier to try and repair by gluing but really would like to find a new switch (as switch took a bit of abuse getting it out) but struggling to find one with same pin spacing.

For the time being have re-assembled the rest of it and tested record OK from the second DIN input (high level on pin 3) which does not go through the Radio/Micro switch.

[David001]

Coming along well. Are the switches expensive?

[DMcMahon]

I have only seen one of possibly the right size and that was in the USA and was very expensive.

Different size ones (not compatible) vary from cheap to quite expensive.

[David001]

Kind of Catch-22, no pun intended

[DMcMahon]

No progress on the switch yet. When I originally took the unit apart, I found that the tape counter plastic mounting was broken off, this explaining why the counter digits and reset bar were at a slant/not horizontal, because the drive belt was pulling on the tape counter.

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.

[DMcMahon]

Originally Posted by DMcMahon

Microphone and DIN line recording not working at all. Microphone/Radio push button input selector switch not staying down/latching in the Microphone down position.

I think the above reference to DIN recording not working only applied to the Radio line input DIN, looking at the schematic again I think the Phono line input DIN should work regardless of what position the Microphone/Radio switch is in.

Was never able to source a suitable push button switch to replace the broken Microphone/Radio switch so plan to just hardwire the associated circuitry for microphone use. Then test phono line in recording.

If it works Ok will do some mono 2 track reference recordings to try out on my Brenells.

[DMcMahon]

Tried Phono line in recording to the Phono DIN socket but no good, nothing recorded (erase works) .

In fact as soon as Record mode is selected get a fixed -6dB signal on the VU meter and the record level control having no effect on the VU meter reading (with or without the recording cable connected).

Also on Playback of old recordings getting a lot of distortion and hum when volume level is increased.

Am hoping this is due to floating circuitry where I have not yet hardwired the Micro/Radio switch .

David

[Uncle Bulgaria]

It sounds like it might be time to try a Uher Switch Manufacture! This could become a habit... I'm trying to stop myself looking at more Uher R2R machines as I still have a couple of 4000 Report-Ls to repair. Those tabletop models look great though. I would like to have a go at a 630...

[DMcMahon]

This time it is not the contact arm but the end of of the operating shaft broken off as detailed in earlier Posts. Previous in-situ glue repairs failed, I may try glue repair attempt again now that the switch is out but not confident of success.

Currently cannot do much at all (if anything) due to serious back pain

David

[DMcMahon]

I see from my Post #7 that I said recording worked from the second DIN input (which is the Phono input).

I cannot now really remember that clearly but if that was correct then something now is different.

[DMcMahon]

Been looking at the broken Microphone/Radio switch parts (as per photo # 1 in Post 7) trying to work out how they go back together before I attempt gluing the plastic end bit back onto the shaft. I thought I had more photos showing various views of the switch when fitted and coming out but struggling to find anything helpful.

Not sure what the copper spring plate is, I assume it somehow fits on the rear face of the front panel and maybe performs the latching of the switch.

Very unsure what the little pin is ? maybe it was soldered in the board and came out when switch was unsoldered but no idea what for.

Will have to have a look at another of my Uhers to see if anything similar.

[Welsh Anorak]

If all else fails you could use a 4PDT relay and a small latching switch on the panel. That switch looks like so many others but when you get down to it they're all different. Any make on it? A Seventies music centre might yield something similar.
Great machine - and a bargain!

[DMcMahon]

Thank you Glyn for the useful suggestion. I think for me personally it would be too much hassle in this case.

There are no markings on the switch, I have the Uher spares listing but it only gives an order number for the switch plus general description.

I removed the switch contact arm from the switch body in order maybe to make it a little easier to glue the end piece back onto the shaft, but when I refitted the arm (still not glued) for testing purposes, it now has got jammed in the switch body. There is a small white semi circular plastic piece in the top entry of the switch that rotates 180 degrees, this maybe is in the incorrect rotational position so jamming the arm.

It is looking like this is increasingly going to be non starter in terms of repairing using the switch so most likely will hardwire the board for permanent microphone connection.

The Radio DIN input is a high sensitivity input that I would not use anyway, would just use the Phono DIN for line input recording.

Still struggling big time with serious back pain so progress on this and anything else will be very slow.

David

[Welsh Anorak]

Makes sense. Maybe a dead Grundig or Telefunken might yield a switch in the future. Looks a nice machine, anyway.