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Old 14th Jul 2019, 2:27 am   #1
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Default Restoring a Sony KV9000UB

Split from this thread: https://www.vintage-radio.net/forum/...d.php?t=157948

The frame timebase is now running. There were two defunct transistors, Q552 and Q553. Q553 is one of the frame output transistors so needs to handle a bit of power and needs to be reasonably high voltage because of its inductive load. I used a BU806 for that. Probably "overkill but I had them laying around. Q552 is a small signal NPN so for that I used a BC337.

There is no raster (yet). I had assumed that might be because of some sort of safety device operating if there is a frame collapse. Next step will be to check the various voltages round the tube base.

C

Last edited by AC/HL; 17th Jul 2019 at 5:57 pm. Reason: Thread split
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Old 14th Jul 2019, 11:37 pm   #2
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Default Re: Sony 2SD625 line output transistor

Latest on the restoration of this KV9000 is that a nice colour picture is now being displayed on this set. The residual fault turned out to be an o/c resistor R353 in the collector of Q305 (pnp transistor). The effect of that was to bias off all three cathode driver transistors so nothing appeared on the screen.

It was then found that the brightness pot itself was o/c from the centre terminal to either side. Disassembly shows the wiper had corroded away. A couple of fixed resistors are currently in place and brightness adjusted by the G2 pot on the tube base. A replacement 5K pot is on order.

I should say that this set was in a very bad condition with a lot of rust on all the metal. The tracks and component markings were invisible on the timebase board copper side. Looks like the set had been in damp/wet conditions. The timebase board copper side was painstakingly cleaned with cotton buds moistened with 50% isoprop.
The screening cans on the main board below the timebase board were very rusty and had to be cleaned. The brightness pot was also rusty and had failed.
I originally bought it only to take some parts from. Tube, LOPT etc but cleaned it up a bit and cautiously applied power. One by one the faults were repaired and the result is a working set.

The set can run from either a 12 or 24 volt battery and at the moment I am running it from a current limited 12V bench supply. Next step is to test out its mains supply, which is a 24V conventional transformer. I am slightly worried about the condition of the mains transformer, given how wet I think this set has been in the past.

Photos attached show it on the bench. The RGB cut-offs and the green and blue drives need to be adjusted.
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Old 15th Jul 2019, 10:56 pm   #3
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Default Re: Sony 2SD625 line output transistor

You're nearly there, well done on the BU806. Sony colour tv's are one of those things I think you need bottle to work on in any depth! Always the best picture in the shop, a trinitron
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Old 16th Jul 2019, 5:30 pm   #4
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Default Re: Sony 2SD625 line output transistor

Thanks Kevin.

Yes Sony kit had a "reputation" for very good kit and well designed. On the negative side, Sony designed their kit from the bottom up and often came up with unconventional designs. Philips were similar in that. If it was a Philips or a Sony you had to get the service sheet out and really study it to get anywhere with fault finding.

I've enjoyed the KV9000 and it does indeed produce a very nice crisp picture. The shadow mask on a Trinitron has the least obscuration of the electron beams of all the types, since it consists of vertical wires.

Shortly will do some electrical safety checks on the mains transformer. The set considers itself double insulated so safety depends on that being OK. As observed before, the set has been very wet and that includes the mains transformer. Not impossible just to run it from an external 12/24V supply or indeed replace the transformer but, if it checks out insulation wise, I'd like to use it.
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Old 16th Jul 2019, 6:00 pm   #5
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Default Re: Sony 2SD625 line output transistor

Nice to see one of these being brought back from the dead - I remember using one as a "what will telly-viewers see?" monitor for some of my early videoconference stuff.

I wonder if it could have been flood-damaged, given the extent of the apparent wettitude? It's not unknown for "white goods", TVs, videos, computers - even cars - that insurers have declared to be a flood total-loss to somehow find their way back into circulation after they've been put in the clearance-skip. I've seen at least one laptop that had clearly been submerged during the 2014 Somerset levels flooding.
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Old 16th Jul 2019, 6:24 pm   #6
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Default Re: Sony 2SD625 line output transistor

They would not have been using water-based varnish when that transformer was made, so it should be fine as long as it is dried out thoroughly before applying full power.
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Old 16th Jul 2019, 8:53 pm   #7
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Default Re: Sony 2SD625 line output transistor

The monitor version of the Sony KV-9000UB, the PVM-9000ME retains the 2SD625 as the horizontal output transistor, but has a two-finned heat sink (bottom right of first photo), compared to the single fin of the KV-9000.

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Old 16th Jul 2019, 8:58 pm   #8
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Default Re: Sony 2SD625 line output transistor

The set is now completely dry. I left it long enough before applying power (12V current limited) to it.

The mains transformer insulation seems OK and it runs on mains. There seems to be a hum bar which seems to be drifting with respect to the picture so probably mains hum. Most likely just the smoothing cap. That didn't show up when it was being run on the 12V psu, of course.

As to the dampness, I was thinking that sets like that were often used in caravans and even boats. Maybe it got left in a damp caravan . The timebase board print side is up, assuming the set was left in its normal viewing position. There is a grill right above the entire board and the print side was covered in "gunge". The component side of the main board (below the timebase board) was also in poor shape and the screening cans were very rusty. The print side of the main board looked like it had just left the factory.

Going to check the bridge rectifier and smoothing capacitor on the mains input side now.
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Old 17th Jul 2019, 2:51 pm   #9
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Default Re: Sony 2SD625 line output transistor

Maarten, I note from a previous thread about early trinitron tubes that a special tool is needed to remove the EHT lead.

I'm sure this is true of my set because I can see the H-STAT feed comes from the tripler unit and there appears to be only one lead. I therefore deduced the lead has to be concentric.

I've had a flashover or two so want to remove the lead and clean/HV grease the area. I also have intermittent sudden changes of static convergence. When these happen, it can be re-adjusted with the H-STAT control. Obviously the problem could be in the tripler but this is a sealed unit.

Any help in how to remove the lead would be appreciated.
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Old 17th Jul 2019, 6:44 pm   #10
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Default Re: Restoring a Sony KV9000UB

Thanks for the pictures Ron. Interesting they decided to increase the size of the heatsink.

Photo attached of mine. I just bent a strip of aluminium I had into a "U" shape. Used a screw through one of the existing holes to secure it. I've now painted it black with high temperature paint.

C
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Old 18th Jul 2019, 6:35 pm   #11
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Default Re: Restoring a Sony KV9000UB

Re removal of final anode and H-STAT lead to the trinitron CRT, I have now managed to do that.

Before doing anything else, I made up a lead to dump the charge on the tube with a 10 meg 1 watt resistor. Drawing a spark to the anode is a bad idea. I have heard that can punch a microscopic hole in the metal, leading to a gassy tube. Unlikely, I'd say, but no need to take the chance. Anyway I don't like loud bangs as much now as I did when younger!

To release the anode connector I simply pealed back the rubber cap enough to see the connector. Then used a pair of fine pincer nosed pliers gently to squeeze the connector. That releases the connector easily.

I cleaned the anode cap rubber and the glass round where it fits. Also inside the anode/H-STAT contact where there is a spring that protrudes from inside the anode connector of the crt.

Refitting the cap is easy, simply press it firmly and it clicks in to the anode socket. Do that with the rubber cap tilted slightly so you can see the spring is correctly placed in the concentric plug. The alignment of the outer part of the concentric plug can be observed before firmly pressing it down. Then I switched on and checked it was working OK. The H-STAT was then re-adjusted. It is advisable to run the set for a while before setting H-STAT as there may be a bit of drift during warm-up. I'm still waiting to see if the static convergence will still "jump".

C
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Old 2nd Aug 2019, 1:36 am   #12
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Default Re: Restoring a Sony KV9000UB

I have been soak testing the set for a while now, never leaving it unattended though. There has not been any recurrence of the jump in horizontal static convergence.

However while watching it recently, there were two or three sharp cracks with visible flash seen through the top. That was followed by the picture disappearing and a puff of smoke.

Once on the bench and being supplied from a current limited supply set to 12V it became apparent that there was way too high a current flowing, though the front neon lamp was on, showing the line output stage was was working. there was an obvious smell of something getting hot so started to trace what it was.

The excess current and smell turned out to be tracking of the 160V winding. That comes from the LOPT and goes to a fast rectifier diode plus inductor/capacitor smoothing. I had noted tracking there before but I thought I had cured the problem by removing some carbonised PC board.
I cleaned it up more carefully and made a slight change to the layout of the copper to increase the separation of the 120V DC from anything else. I know the board had been very wet in the past. I also heated the board to drive off any moisture on it.

Result; no tracking and the input current returned to normal, well a bit below normal actually. There was also was no picture! Looked like the arching had taken something else out - but what!

Well we all know what causes no raster in a TV. Hmm, just about everything I hear everyone saying.

I rapidly checked there was line output, and frame time base was also OK. So its probably a CRT bias problem. As the LOPT was not in distress and supplies derived from the LOPT were all normal I made the assumption that the EHT was OK. I do have ways to check that, but I decided to take it as read that it was OK.
Checking the RGB video drive transistors (on the CRT base) showed they were ALL high - enough to be cutting the tube off. OK, so look at the drive transistor emitters, which are connected together and driven from the main signal board through Q305. When I first repaired the set the emitter 39 ohm resistor was O/C. The voltage on the video output transistors was correct.
Then checked the base voltages and they were ALL well below correct at about 3V. The base voltages would vary when the appropriate R,G or B level pot was varied, but up to a maximum of only 4V. So all three transistors were biased off.

Next look at the base drive wave form. This is derived from IC 302. The drive wave form was OK, but its static DC level was incorrect, too low. This was true for all three drives.

Flash-overs can cause lots of damage and can take out multiple transistors so got to suspecting maybe all three video output transistors could be damaged. One was removed and the base voltage where the transistor was measured. The thinking being the (failed) transistor might be holding the voltage from the IC down. Not so, it was still low on the base of the removed transistor. The removed transistor was tested and found to be OK.

Has to be something else, but what?

Don't know it I'm "allowed" to do this but this is getting long. So I'm going to continue this with part two and will reveal all...

Love to know what you think I checked next and what the fault was?

C
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Old 3rd Aug 2019, 4:55 pm   #13
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Default Re: Restoring a Sony KV9000UB

OK, here is part two and "the answer".

The fault was probably provoked by the arching incident on the timebase board. The thinking is that that involved the 120V supply and the arching would have intermittently loaded the line output transformer. It supplies 12V to the signal board where the RGB drives are (not the video outputs, they are on the CRT base).

If there had been any spikes on the 12 V line, that could have stressed components on the signal board. The most depressing thought was damage to IC302 which provides the RGB drives. All thee were low BUT the waveform of that drive was NORMAL.

Hmm before accusing the IC, I got to thinking about how the black level clamps work. They set the black level (DC restoration) by reference to the sync tips. So it would be a very good idea to check the output from the sync sep, wouldn't it?

The circuit shows there should be 3.2V on the collector of Q304 (sync sep). The actual reading was a nice ZERO. More or less certain the transistor had failed so out with the desoldering pump and careful removal. Its pnp so off to my spares rack for a suitable replacement. Not really anything special about it so used a 2N3702.

A nice blue picture came up and rather too bright, so switched off again quickly. The reason for the blue picture was just that I had turned up the blue and green drive pots to max to try to produce a raster. No green because I had removed the green video output transistor to see if that had any effect on the drive voltage from the IC (which it didn't).

Re-fitting the green video output transistor and putting all three drives amidships switched on again. Up came a reasonable picture. A few tweaks of the drive pots produced a nice picture.

I've been soak testing the set again a fair bit. When I'm working at my bench I have it on so I can keep an eye on it. Fine so far...
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Old 13th Aug 2019, 12:30 am   #14
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Default Re: Restoring a Sony KV9000UB

I have two of these sets and the one sold as "working" turned out to have a sound fault.
The symptoms were no sound until the volume was very near turned up full, then only weak sound at top volume.

I assumed this was the pot, which was also very stiff to turn. I gave it a spray with switch cleaner and turned it from min to max until it eased a bit. The fault remained, so looked at what waveform was on the top of the pot. Result, none just 12V DC. OK, its a Sony so need to look at the circuit. The pot just delivers 0-12V to pin 13 of the audio IC 203 through R244 (1K). There is a 10uF electrolytic to 0V from pin 13. I replaced the resistor and the capacitor. This needs the screening can over IC 203 to be removed. Once replaced found the fault remained. I thought the capacitor was a good candidate and the 1K unlikely but did both while I had the set apart.

Back to the circuit and now did what I should have done before (as we all know) which was to check the voltages on the IC. Pins 12 and 14 should be 11.5V but were 4.5V. Looking at the circuit I immediately suspected R240, a fusible resistor in the supply line to the IC. It should be 39 ohms and I remember just such a 39 ohm resistor was o/c in my other set in the video output section. Sure enough R240 was way higher than 39 ohms. Replacement restored normal sound.

R240 is shown as a special device, acting as a fuse, so exact replacement is slightly problematic. I replaced it with a 1watt metal oxide type and spaced it off the board to the same extent as the original.

Last edited by space_charged; 13th Aug 2019 at 12:41 am.
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Old 21st Sep 2019, 4:50 pm   #15
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Default Re: Restoring a Sony KV9000UB

I have just about finished with this restoration. One of the sets had a problem with intermittent changes of horizontal static convergence, H-STAT. With these early trinitron tubes, H-STAT is achieved by a variable voltage applied at almost the full EHT (nom 17.5KV). This is delivered by the "HV block" which houses the tripler. H-STAT comes from a pot with resistors either side across the final stage of the multiplier. Its all sealed, potted in epoxy so highly resistant to repair. The H-STAT voltage itself is delivered to the concentric final anode connector on the CRT. The EHT lead is co-axial with the H-STAT voltage the inner wire and the EHT the outer.

I found that just by running the set for a long time that this "jumping" of H-STAT gradually decreased and now seems to have gone. Possibly some residual moisture has been removed by heating and/or action of the EHT on it.

Ideally I'd replace the HV block, and web searches do show Sony parts coming up from time to time. The part number I searched for was Sony HV block 1-453-050-31. Nothing so far but I'll keep looking.
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Old 26th Sep 2019, 6:40 pm   #16
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Default Re: Restoring a Sony KV9000UB

Thanks for the help in the "items wanted" section on the Sony HV block for this set.


It looks like the HV block in a Sony KV6000 is similar to the one in the KV9000. Looking at the circuit, it seems to supply the H-STAT voltage from a potential divider across the entire EHT.

It might be possible to make up such a divider for my set. Sadly none of the circuits give the values for the resistors. I may be able to deduce the values from external measurements on the HV block. Failing that, data for the trinitron would tell me the voltage range for the H-STAT electrode.
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Old 28th Sep 2019, 1:09 am   #17
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Default Re: Restoring a Sony KV9000UB

The existing HV block seems to have settled down and H-STAT hasn't been seen to "jump" the way it was doing. If I'm lucky it might be OK.

Here is a photo of it in my kitchen.

The other pictures show the concentric EHT lead. The inner is the H-STAT voltage which is variable and only a few hundred volts below the full EHT (17.5KV). The red object is the HV block which supplies EHT, H-STAT and the focus voltage.
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