1988 Philips 2B goes into protection mode, whistles

[Nickthedentist]

So pleased you got it going!

You're very lucky to have a "loudspeaker repair shop".

Shame about the lack of NTSC decoding, but maybe you will be able to sort that out one day.

Nick.

[Maarten]

I'm not sure, but it might be possible to fit the decoder from a 3A chassis. 3A sets were always fitted with a multistandard decoder, while 2B sets were PAL-only for versions /00 and /15 and PAL/SECAM B/G for version /02. I'm not sure which versions sported a multistandard decoder.

[133MHz_]

Thanks to work and a fairly long national holiday progress has been rather slow but good nonetheless. Even though there are still some issues, I've been able to sit down and enjoy this beautiful set, so once again thanks to Richard and Symon for pointing me in the right direction.

Originally Posted by Philips210

I was wondering if your original LOPT is faulty after all. It would be interesting to compare ring tests on the two transformers, though insulation breakdown in normal operation can't easily be simulated.

Unfortunately it is indeed faulty. I know a place near me which sells replacement parts for LCD TVs and such but the guy running it still keeps an old LOPTx tester and will test yours for a very reasonable fee, so the first thing I did was to bring it to him and get it tested. I believe his tester just drives/loads it like a TV would and measures the EHT. He told me the thing was basically one big short circuit.

From what I've read these are very failure prone, which makes me wonder if the HR replacements may be more reliable than the original Philips parts. I surely hope so!

One thing I didn't tell you about the original EHT lead. Before I got the chassis running I went ahead and performed a crude 'insulation test' on the lead using the EHT generator from a broken plasma ball ornament, which is pretty much a small flyback type transformer (probably without a built-in rectifier) and a self-oscillating driving circuit. Judging by the length of the sparks I can draw I believe it outputs 12 to 15kV (if the dielectric constant of air figure of 3kV/mm I've read is correct), but going by the sheer size of the transformer it could be as low as 5kV. I connected the EHT output to the part that goes into the LOPTx and hovered the return lead close to the anode cap connector - drew a small-ish spark. Did the same to the outer braiding of the cable (which is normally grounded to chassis)... much bigger spark! I conclude that either the insulation on the EHT lead is internally punctured (and this could've killed the original LOPT) or my crude testing procedure damaged it somehow (unlikely since the EHT should be much lower than normal). Either way I don't trust it so I'm using a typical red one cut off from a scrapped chassis of the same tube size.

Originally Posted by Sideband

You may well find that the other problems will be cleared by replacing any electrolytics on the supply rails. Some of these must have dried out by now.

I've followed your advice and replaced the electrolytics on the frame output stage, the main filter capacitor and nearly all the ones on the secondary side of the power supplies (SOPS and LOPT) and the linearity problem went away for good. The only ones I didn't replace were the two 47µF 160V for the +140V rail because I noticed the ones I got from the shop have dents on the cans (which I believe could compromise internal insulation) so I'd rather get new ones, which gets me to...

Originally Posted by Nickthedentist

You're very lucky to have a "loudspeaker repair shop".

Yeah I believe I'm very lucky to have several local electronic parts shops where I can get components right now and not having to wait by ordering online, but the downside is that all of them seem to stock very low quality Chinese electrolytic capacitors. I've already had bad experiences with them. A while ago I recapped a ~1986 Noblex TV and the two Nichicon 100µF 160V caps I got for the HT rail looked suspiciously small for their rating and the print quality looked rather shoddy, which made me believe they could be counterfeit but I used them anyway. After about 3 hours of watching said TV the raster collapsed followed by a loud BANG! and a big cloud of smoke poured out the back, both new capacitors went short circuit and burst. I put the original Samsung ones from the 80s back and it just keeps on going!

These modern Chinese capacitors are garbage, in fact I just caught one going bad on this TV, which I haven't used more than 5 days since I've recapped it! I took the chassis out today and spotted one of the new 1000µF 25V on the power supply rails already swollen, unbelievable. Good thing I caught it before it went bang like on the other set, check out the attached pictures. So now I've got to replace them, again.

As for the other things, I'm still having EEPROM issues (which is why I pulled the chassis out today). I found out that channel presets are stored correctly but brightness/contrast/saturation settings are lost immediately when powered off, not even kept if maintained on standby, which is a huge pain since the default settings are way off. I pulled both 24C01s to test/dump them with my EPROM programmer and found out that only the chip on the position 7925 (all address lines tied to ground) is getting written to, the other one (A0 tied to +5V) is empty and the chip itself is good. I'm going to try fitting a single 24C02 instead and see if the set manages to write the full 2KB to it, and if that doesn't work, it's back to the battery backed-up memory.

[Maarten]

The bigger spark could be because the EHT lead is basically a capacitor.

[davegsm82]

Originally Posted by 133MHz_

From what I've read these are very failure prone, which makes me wonder if the HR replacements may be more reliable than the original Philips parts. I surely hope so!

One thing I didn't tell you about the original EHT lead. Before I got the chassis running I went ahead and performed a crude 'insulation test' on the lead using the EHT generator from a broken plasma ball ornament, which is pretty much a small flyback type transformer (probably without a built-in rectifier)....

Nope, those plasma balls work on AC, it's the capacitive effect of your hand on the glass that allows current flow, wouldn't work with DC, so don't get caught out by this

Dave.

[Welsh Anorak]

Hi
I'm sure your "Nichicon" capacitors weren't genuine - it's very rare to have one fail even after heavy usage. Along with Panasonics they are the ones to use - and obviously ones for the fakers to make! Luckily we don't seem to have many fake capacitors in this country.
Well done on the TV - I've always found the HR transformers to be extremely reliable and were a pattern part I was always happy to use.
Glyn

[Michael Maurice]

For the batter you could try using a super capacitor.

First measure the old battery and with the set switched on, measure the voltage across the battery connections on the PCB. Make sure its around 1.2V (or 2.4V if its the bigger battery).

Assuming its correct, you could fit one or two super capacitors of say 10F http://uk.rs-online.com/web/p/electr...itors/8087976/

That should do the job