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Old 23rd Mar 2021, 12:02 pm   #1
3CX15000A7
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Default Restoring a CP110, tube life after regeneration?

Hi all,

I couldn't resist to buy another CRT. This time a 27CE3591 out 1987, one of the first CP110. It's fitted with a A66EAK51X03 tube.

After first powerup, the picture was dull with low contrast, very bad convergence and all kind of electronic picture faults.

I got a müter BM95 rejuvenator for a low price and I measured the tube. I got for RGB respectively 0,7mA, 0,6mA and 0,5mA. I did the gamble and started the (automatic) rejuvenation. Results where good, red and green around 1,15mA and blue around 1,05. Life test did increase the current very little, around 0,05 - 0,1 mA

It seems very succesful, the contrast, colors, convergence, focus all seems very good now.

What is your expierence with this type of tubes? Will it last some time? I see a lot of expierence of rejuvenating older 30AX tubes, but what about those?

I still have a lot of challenging electronic failures to find but I will wait a bit to see if I can find it myself before asking for help. Al lot of dry solder joints on the CRT panel for sure, and a lot of caps . .
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Old 23rd Mar 2021, 2:10 pm   #2
Welsh Anorak
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Default Re: Restoring a CP110, tube life after regeneration?

This 45AX CRT is usually very reliable and long-lived. The fact you had poor convergence suggests to me that you had a partial short in the gun assembly that the rejuvenator blew away. In this case I'd expect a long life out of it again, but you never know...
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Old 24th Mar 2021, 7:11 am   #3
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Default Re: Restoring a CP110, tube life after regeneration?

Hi Welsh,

A partial short, between which elements could that be? And how would that affect convergence? (just curious)

I also have a newer type 45AX tube (blackline one in a md1) which have excellent emission (more than 1.1mA each gun) but pretty bad focus at the sides. Do you think a rejuvenation could help this tube too?
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Old 24th Mar 2021, 9:44 am   #4
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Default Re: Restoring a CP110, tube life after regeneration?

To be honest I've no idea either - perhaps someone else would know why? I assume it's a problem with the focus electrode. I suppose now they are a few years old odd things can happen. Back in the day I only experienced focus problems with the 21" 45AX tubes - the larger ones were pin-sharp.
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Old 24th Mar 2021, 4:25 pm   #5
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Default Re: Restoring a CP110, tube life after regeneration?

A dull pic on these was often dueto a bad cap on the HT line. 22uF if I recall.
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Old 24th Mar 2021, 5:18 pm   #6
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Default Re: Restoring a CP110, tube life after regeneration?

Yes, and there was a beam limiter fault that did the same. However that wouldn't account for the poor focus and misconvergence.
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Old 25th Mar 2021, 10:00 am   #7
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Default Re: Restoring a CP110, tube life after regeneration?

For sure it was the tube, before I started the rejuvenation I shorted the coil in series with the heater that fixed the dull (but also convergence) problem.

For now I have three main faults left in the set:

- Vertical lines start rippeling after warming up slightly. Even after replacing the well known C2670/C2621/C2633 and R3628 (someone else placed a wrong resistor there). using coldspray I located that the fault is at the IF/SYNC module, seems I have to overview that toroughly

- Vertical linearity is bad, top and bottem are cramped, but the middle is strechted out. Not very badly but pretty noticable with vertical pans. C2573 (replaced), C2575(replaced), C2574(replaced), R3575, R3574 seems all be good . .

- But what really puzzles me is the +210V. The picture has some smearing and very mild colour flashing. The known R3415 around T7413 is OK, even is capacitor C2405. I all resoldered (completely removed old solder as it really doesn't want to flow again) this circuit.

Looking Furhter, the +210V seems too low, around 190V, measured at the connector on the tube PCB and not fully stable. C2406 and C2638 measure good. G2 Also the LOPT (core) get's very hot, I cannot touch it after a hour on time) . .

Someone an idea about this last problem?
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Old 25th Mar 2021, 10:26 am   #8
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Default Re: Restoring a CP110, tube life after regeneration?

Not too happy about the LOPT - could the core be cracked? Might be worth taking it out to have a look - it certainly shouldn't get that hot. You could disconnect the 210v feed to see if that's somehow loading it, but 190v seems OK.
The capcitors in the IF unit are well known for drying out and are easily replaced.
Don't forget the LOPT might be working ar reduced efficiency so the frame stage voltage might be a bit low causing the poor linearity.
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Old 25th Mar 2021, 10:42 am   #9
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Default Re: Restoring a CP110, tube life after regeneration?

For vertical: In the schematic I see only +140V (is OK on DC meter) and +32V , both seem to come directly from the main PSU. The +32V has a ripple of 1V pk-pk measured at C2574. Measuring with the scope at "33" (C2589) cleary shows some bending on the start/end of the line.

For +210V (and +140V) I will make some scope measurement photos. I have the idea the color isn't very pure because of the varying +210V on the cut-off circuit. Also strange is that I cannot crank the G2 to the point you get the lines and the white screen. Maybe also an indication for a bad LOPT . .
HT otherwise seems stable, picture sizes doesn't change really with varying content and no blooming.

I have to say, this set is misused, the beam limiter was bypassed on some way it wasn'n functional anymore. I found out after rejuvenating the tube that whites where extreme bright and flashing. Maybe this damaged the LOPT and some other stuff . .
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Old 25th Mar 2021, 7:34 pm   #10
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Default Re: Restoring a CP110, tube life after regeneration?

Some scope measurements(left to rigth)

140v ripple (2v/div 5ms)
140v ripple (5v/div 50us)
210V ripple (5v/div 50us)
32V ripple (.2v/div 5ms) (seems modulated by vertical)

Are this normal ripple voltages for the supplies? Looks like

One correction, the 210V drops after the R3445 to 190V (from 203V), maybe afterall not so strange . .
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Old 4th May 2021, 5:19 pm   #11
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Default Re: Restoring a CP110, tube life after regeneration?

Quote:
Originally Posted by 3CX15000A7 View Post
Hi Welsh,

A partial short, between which elements could that be? And how would that affect convergence? (just curious)

I also have a newer type 45AX tube (blackline one in a md1) which have excellent emission (more than 1.1mA each gun) but pretty bad focus at the sides. Do you think a rejuvenation could help this tube too?
Hi,

Still fighting with the cp110, but in meanwhile I worked also on the md1.1. Afterall, it was a gassy tube. Beside the bad focus it also had problems with color smearing, some change in the caps at the emitter of the rgb drive improved things a bit, but focus remained avarage.

While Removing (carefully) the crt panel to try a rejuvenation, i heard some sissing/ticking noise. I think it was already leaking for a long time a very little, but removing de CRT panel made it worse so does the focus . .

End of the story for the md1 sadly . .
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Old 11th May 2021, 2:24 pm   #12
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Default Re: Restoring a CP110, tube life after regeneration?

Hi all,

In meanwhile I did a nearly full recap on the CP110 set and soldered the whole tube neck board again! (it was full of bad joints)

I still struggle to get a OK/good picture, with a lot of odd picture faults (ghosting, moire, linearity issues etc.)

So I decided to go back to the basic, the PSU and line stage. The 12/15V/32V seems OK, but I found some odd behaviour in the line stage.

Measuring at the base of the Hdrive transistor (T7630) I get some strange ringing at the square wave that shouldn't there according to the service manual. I disconnected the H deflection coil to check the stage around TDA2579 and it dissapeared (I got a nearly perfect square wave).

Any ideas where the ringing comes from? Can it be the diodes D6610/D6609? Wondering if this causes also the hot running LOPT . .
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Old 12th May 2021, 4:20 pm   #13
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Default Re: Restoring a CP110, tube life after regeneration?

The +B line calls for low ESR / high ripple capacitors, but I doubt that's the cause for this issue.
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Old 14th May 2021, 10:20 am   #14
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Default Re: Restoring a CP110, tube life after regeneration?

Hi!

Meanwhile I replaced the diodes, but this didnt changed the ringing/hot LOPT.

I found a solution to one other problem: the shaky/ragged vertical lines. I already replaced the known caps on the B+ line (with low esr ones!) and driver stage but that doesn't solve it.

This problem was caused by the IF chip (TDA2541) or something around throwing HF distortion on the +12v locally

removing this chip solved the problem (I use only scart so not a big deal) and improved the horizontal stability and also the color seems more stable now.

It didnt fix the ringing/lopt altough. I ordered a spare LOPT to see if things improve . .
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