Grundig CUC 220 Restoration

[andyw25]

Hi All

Been awhile but picked this back up, have gave the set a thorough going through, full re-cap, re-soldered all joints etc. However the neck board looks a little odd, as though it's melted at some stage. I've attached some pictures, what does everyone think?

Should it be okay or should a replacement board be sought, I'm not entirely sure what the melted plastic part is, it would appear the blue wire from the Tripler goes into it?

Excuse the brown mess everywhere, it must have belonged to a smoker, tar everywhere which has taken a lot of cleaning to improve.

Kind Regards, Andy

[dazzlevision]

The white box is the focus electrode spark gap and the white blob may just be silicone sealant.....perhaps applied by a previous repairer in order to stop corona discharge or flashover....?

I'd carefully clean all that tar deposit off or you may have tracking/arcing problems.

[Welsh Anorak]

Actually, ISTR that was how they all were.
I'd give the base a good clean - I can almost smell the tarry mess you'll have to deal with! Luckily very few sets have that nowadays.

[Nickthedentist]

Yes, obviously a smoker's set. I wonder whether it's lasted longer than the owners did?

[Maarten]

Speaking of smoke... Be aware of any paper capacitors in the mains filter and line output. Marcel (marcelstvmuseum) had a Philips set go up in flames. It had a RIFA filter capacitor right where the fire seems to have started. White three legged capacitors such as used in German sets were already known to cause fires back when the sets were in daily use. I think Grundig used slightly better ones, but they will be tired by now as well.

[ben]

I'd take that neckboard off completely and soak it in water and vinegar or something. Any gunk there will give trouble.

The last of my CUC220s I worked on had tripler trouble, does your deflection work?

[its ur aerial]

I once found the arcing in the focus spark gap of a Grundig, caused by a spider that had crawled in there, and obviously meet his maker.
But, yes that dollop of Silicon was normal, give it a good clean, remove any carbon and nicotine.
All Spark gaps were a common cause of arcing back in the day.
Ken G6HZG.

[andyw25]

Thanks for all the advice everyone.

Indeed the set must have belonged to a smoker, now deceased as it came from the cupboard of a house that was being cleared. Every single board on the chassis was a tarry mess. I've removed each individual board and thoroughly cleaned, re-capped and reflowed each one. Just finished re-capping and reflowing the main chassis over the weekend.

The tripler was horrendous, absolutely covered in a thick tar, took ages to clean off but I have a couple of NOS ones if necessary.

Hopefully be able to get it back together this week fingers crossed. Pictures to follow.

Incidentally does anyone happen to have a spare Tuning Module, part no 29504-003.02 as the backup battery has caused more damage than I had thought, quite severe corrosion to both sides of the board and traces. I can probably patch it up if all else fails

[ben]

Why did you 'recap' the whole thing?

[andyw25]

Maybe slightly exaggerated there, not quite a full recap but replaced most of the old ERO/Frako caps as quite a few were bad.

Got it back up and running today and still suffering with an issue, there seems to be lack of red in the picture, any suggestions where to start?

[Welsh Anorak]

Start on the CRT base and see if the red cathode's voltage is higher than the other two. Hopefully it is and we can eliminate the tube.

First off - how's the black and white picture? That will tell us if it's a decoder or RGB output stage fault.

Report back and we can guide you in the right direction.

[andyw25]

I'll check that next, I'll dig the service manual out, do you know off hand where I would I check for the voltages on the base?

The black and white picture is currently green There was a damaged trim pot on the rgb board but I haven't any replacements of the same value. I do have a spare RGB board from another CUC chassis although it's slightly different, has PAL - NTSC wrote on the board, it does fit however?

[Welsh Anorak]

It's certainly an output stage fault then. Hopefully the CRT is OK. First thing is to replace that trimmer - your spare board could well yield one. That will be a drive control, and if broken could well be the souce of the problem.

The cathode pins on the CRT's base depend on the CRT fitted - your manual will give the correct pins. It shouldn't be too hard to work out which is which as there should be three pins at around 130v. Chances are one of these three will be nearly 200v. The other pins will be heaters (no sensible DC reading) and G2 (high reading, in the region of 500v) so a process of elimination will give you the correct pin.

Not sure if the PAL/NTSC board will do, but it's worth a go.

But change the preset first!

[andyw25]

The mystery deepens. Replaced the trimmer with a spare. No longer green, however there is no colour. I can adjust the greyscale blue or green, no red still. But when the colour is turned up there's no colour picture, remains black and white.

Swapped to the PAL/NTSC spare RGB board, and it behaves in exactly the same way.

[Welsh Anorak]

Now we get deeper. You're tube's good, so that's nice. The fact both boards exhibit the same fault suggests perhaps the DC level adjusted by the colour 'control' is low. You mentioned there had been corrosion damage to the control board, so best check here first.

Memory doesn't serve and the manual's tucked away somewhere - is there a separate decoder or is it a combined decoder/RGB panel? Photos would help.

No offence, but how familiar are you with decoders? Don't forget the decoded chroma is added to the luminance so a variation in colour when the colour DC level presets are turned is to be expected reghardless of the presence or absence of decoded chroma.

[andyw25]

So, as suggested I've had a good look at the control board that had the corrosion. Swapped this with the spare from the parts chassis, again this appears to be from a foreign market set but even with this board swapped, no change, fault remains the same.

I'll attach some pictures, the pictures showing channel 82 are using the spare board and pictures showing channel 1 are using the original board.

I know the tuner/IF modules on these caused issues, but I've already changed the electrolytics in there and checked/reflowed joints etc according to the service bulletin. Also can't figure out where the horizontal adjustment is as you can see it's not quire correct.

I'll attach some pictures of the RGB board, can't see anything in the service manual referring to a Decoder so I'm assuming they are combined but I'm not sure, I'm not very familiar with decoders.

[Sideband]

That doesn't look very black and white to me! More like black and cyan. I don't think there is any red drive so it's back to checking tube voltages. Can we confirm the tube base voltages first?

[ms660]

Originally Posted by andyw25

I'll attach some pictures of the RGB board, can't see anything in the service manual referring to a Decoder so I'm assuming they are combined but I'm not sure, I'm not very familiar with decoders.

Yes, the colour decoder is on the board in the photo you posted, it's the TDA3561 IC (IC 2515) in the schematic I'm looking at, the RGB outputs to the driver transistors (which feed the cathodes of the CRT) are pins 12, 16 and 14 of the IC respectively.

Lawrence.

[ms660]

Originally Posted by ms660

Yes, the colour decoder is on the board in the photo you posted, it's the TDA3561 IC (IC 2515) in the schematic I'm looking at, the RGB outputs to the driver transistors (which feed the cathodes of the CRT) are pins 12, 16 and 14 of the IC respectively.

Whoops...that should be pins 12, 14 and 16 respectively for RGB.

My apologies.

Lawrence.

[andyw25]

I'll test the tube base voltages in the morning, and see how things look there before re checking the rgb board. Hopefully it's something simple, as I'm sure it had colour before