Uher CG 310 Cassette Deck Check Out

[DMcMahon]

This late 1970's stereo deck is my latest acquisition, it was sold as all working with 1 defect, the left channel VU meter lamp not working.

I think a nice looking deck and in pretty good condition.

It is a more basic version of some of the similar decks in the 3XX & 4XX series, a pretty rare model in the UK I think.

Opened up to check internals before powering up, all clean and tidy inside, lots of plastic gears on the drive mechanisms. Think the VU meter bulbs must be behind the metal covers above the VU meters as per third photo

After replacing the 13 amp fuse in the mains plug with a 1 amp, powered up all OK.

Playback and line (DIN) recording all work very well, it sounds very good. At one stage I lost the right channel both on playback and record, not sure what was going on there, if an internal intermittent fault then could be difficult to track down as cannot find a schematic.

All tape transport controls work well. Microphone recording still to check.

So overall looks a good buy so far.

David

[DMcMahon]

Removed the front panel to see if could see/access the left hand VU meter lamp that is not working, was able to see/access OK. The lamp was protruding out noticeably compared to the right channel lamp, I pushed it back, initially assuming it was a push socketed lamp but still no good.

Looking from the top realised that they are wired grain of wheat lamps so not socketed.

By measurement and examination under magnifying glass confirmed that the lamp filament is open circuit.

Measured the lamp voltage supply as 16.5VAC, I have some grain of wheat lamps but at a much lower voltage but will try one when I find them.

Tried to measure the current on the working lamp to get an idea of wattage/current rating of the lamps but could not get a reading ?

David

[Nickthedentist]

Did you try with your meter set to ac and dc?

Nice looking deck!

[DMcMahon]

Yes I did Nick, yes I like the look of it and it does perform well.

Discovered that the Parkside TRMS Digital Clamp Meter I was using (fairly recently purchased from Lidl after reading about it on a Forum Thread) only measures AC current via its clamps, i.e. not by its meter leads (I was connecting the leads in series with the lamp).

Using another meter measured 43mA AC.

David

[DMcMahon]

Originally Posted by DMcMahon

Yes I did

David

Actually not until I tried another meter because the Parkside meter does not measure DC current. When I initially tried the other meter I got zero mA on AC and DC and the lamp did not work, stupidly I had forgotten to switch the Variac back on !!

With power on and lamp working (43mA AC), DC current measured zero.

David

[Uncle Bulgaria]

It seems funny the lamp voltage would be 16.5V. Surely with this being the same year as the CR 240, which uses 3V/30mA grain of wheat bulbs, they'd not have wildly different but similar looking components knocking around. Is that a circuit note or measured data? If the latter, could it be wrong?

[DMcMahon]

No schematic unfortunately, measured voltage across both lamp wires.

I see you can buy 16V grain of wheat lamps.

I know what you mean but I am not that surprised that they used different voltage lamps

Found my spare grain of wheat lamps they are only 6V.

David

[DMcMahon]

Found a schematic for a CG 320 (not similar styling).

This uses a bunch of 16V/40mA lamps (type unknown) for various indicators but fed from +14.5VDC supply. Have not yet spotted the VU meters on the schematic though.

David

[DMcMahon]

Traced the VU meter lamps wiring back to the board. 2 pairs of black wires connect to 4 points on the board identified as "PL1" and "PL2" (no pug/socket connection), these 4 points are paralleled and connect directly to the AC input of the bridge rectifier. The bridge rectifier AC input is fed from the mains transformer via a 630mA 20mm glass fuse.

The bridge rectifier output is +20.3V

So happy that the VU meter lamp supply is a nominal 16VAC

Out of interest tried a 6V grain of wheat lamp on the left VU meter, as expected it is a lot brighter than the right lamp. Only took the mains voltage upto 120 volts as it looked like the 6V lamp would not take a lot more voltage (8 volts at the lamp).

David

[DMcMahon]

Looking to find suitable 4mm/16V/40mA grain of wheat lamp, not easy to find that combination and most of them come from China.

While tidying up the lamp wires from the tests, the right hand lamp metal housing fell off so glued it back on.

David

[Uncle Bulgaria]

Possibly these might be suitable?

[DMcMahon]

Well found, thank you very much Uncle Bulgaria, I have placed an order.

David

[DMcMahon]

Replaced the blown left VU meter bulb. Brightness level very similar to the right so will not bother also changing that one.

David

[Uncle Bulgaria]

That looks great! I trust the instructions have the same comprehensive level setting instructions as in the Uhers I've looked at?

[DMcMahon]

Originally Posted by Uncle Bulgaria

That looks great! I trust the instructions have the same comprehensive level setting instructions as in the Uhers I've looked at?

Unable to find any documentation for it.

David

[Cobaltblue]

Re opened by request.

Cheers

Mike T

[DMcMahon]

As per Post 58 in my Wow & Flutter Thread after creating a test tape the tape transport totally stopped working, so will need to open it up to see what has happened.

https://www.vintage-radio.net/forum/...d.php?t=193107

The right VU meter bulb is not working, had previously at Post 13 replaced the left VU meter bulb so have some spares if it is the bulb that has failed.

David

[DMcMahon]

Removed the top cover expecting to see a broken drive belt or worse still a broken plastic gear but from first quick perusal nothing obvious untoward.

But when I manually rotated the capstan flywheel I could see a small white double ended plastic gear flopping around, impossible to see why but would imagine that its mounting shaft has sheared.

Need to work out how to strip it down sufficiently to see better.

David

[Uncle Bulgaria]

Do you think your decks are trying to tell you they need to be on permanent display and resent being in the loft?

[DMcMahon]

Yes quite possibly, I wish I had the space to put a fraction of them on permanent display

David