CurtPalme.com Home Theater Forum

[draganm]

so as some of you probably know I re-furbish/upgrade boards but I don't do repairs. Have no desire to either but I inadvertantly wound up putting time and money into a CVA with a dead blue channel Horizontal channel.
no problem I thought, I'll repair just this one. replaced all the power transistors for 20+$ , nothing. Took another bad board and swapped all 16 FET's over, nothing. checking diodes over and swap a few just for the hell of it, nothing Mind you by this time i've put a meter on every f-in little part at least 3 times, even swapped a few ceramic cap's, STILL nothing

then last night I see the 2 little resistors E-home installed sticking up off the board like dead bugs. nothing special, 61 OHM 5% 1/8th watt little sh*t part. So going by that, the limit should be 58 to 64ohms. Technically at 67 ohms they're all out so I figure the one reading 69 ohm's couldn't POSSIBLY be it. I swap it out and lo and behold the channel works.
Why the HELL would they skimp on this part if it's that sensitive? the very best 1% 1/4 watt precision resistor from Mouser is 5 cents? I've actually come up with a mathematical equation for this 5 cents + 2 ohms = 14 hours.
I can't belive Curt does this for a living, I would go insane.

[StylinLP]

Hey Dragan. Can you replace my two resistors too? lol

[SisterOfMercy]

Of course Curt is psychic.

I've never encountered 61 ohm resistors, only what exists in the E-96 series. Are you sure it's 61 ohm, not 68 ohm?

[Nashou66]

Fun diagnosing problems at the board level isn't it drags I still have a FCM I want to conquer, Not that I really need it but just the point of doing it, I hate giving up.

NOT!!!!!!

Athanasios

[draganm]

[_in_peace_]

hehe it sounds like lottery business!
But you should be proud that fixed the problem in the end

[stefuel]

Buy a AmPro and you won't have to put up with all that schit.

[Curt Palme]

[Curt Palme]

[Curt Palme]

BTW, I don't buy that a resistor out by 2 ohms caused a convergence amp to fail. There are a bunch of fusible resistors on that board that blow open when an overload condition is seen (or a tube arc, or ???), but it's a fairly standard amplifier configuration, 2 ohms out would not cause failure of the amp. (IMHO).

Also, JOhnhwman has my total respect when it comes to PC board repair. I'm really good at analog circuits, but he's got it down flat when it comes to digital repairs, something that is beyond pure logic in my opinion anyways.

[Curt Palme]

BTW, I don't buy that a resistor out by 2 ohms caused a convergence amp to fail. There are a bunch of fusible resistors on that board that blow open when an overload condition is seen (or a tube arc, or ???), but it's a fairly standard amplifier configuration, 2 ohms out would not cause failure of the amp. (IMHO).

Also, JOhnhwman has my total respect when it comes to PC board repair. I'm really good at analog circuits, but he's got it down flat when it comes to digital repairs, something that is beyond pure logic in my opinion anyways.

[macgyver655]

[Curt Palme]

I'll see if I still have the board. It's an H output board from a 3600. It caught fire, and I guess it smoldered long enough just not to blow whatever fuse would protect it. It cooked the board bigtime. I saved it for the capacitors, there were actually few parts blown on the board, but enough to make it a Curt 'classic'.

Now, to be fair, I've had my own personal Barco retro 808 do the same thing, a glycol leak into the convergence board multipin connector smoked it and blew a hole in the board as well, but I repaired that one.

I don't think an NEC has blown a board up, but I do have a motherboard from a 9500 Ultra that also fried a few traces making it beyond repair. That was a glycol leak as well.

The best one ever though was non CRT related. We sold a first generation Stewart power amplifier into McDonald's corporate boardroom, I think in 1992 or so. It used a switching power supply, much like the Marquee that was auto switching from 100 to 240 volts. Very lightweight, about 20 lbs or so, 100 watts per channel. We got a call about a week after we put it in: 'Umm, there's a really bad burning smell in the boardroom, and we think it's coming from the sound system'.

We get there, and the boardroom opens up into a big atrium where reception is. 20' ceilings, etc. The whole damn place smells of burnt silicone.

The Stewart amp had smoked, and as with the Ampro, didn't blow the fuse. We were reallly embarassed of course, pulled the amp and put another one in. IN the shop, I opened the amp, and it was divided into 2 sections, the switching supply and the audio amp section, separated by metal shields due to the noise that the switching supplies put out. I swear, it looked like a bomb had gone off in the switching supply section. I mean, I opened the amp, and a puff of burnt silicone/fibreglass floated out of the amp. Everything was black and charred. I couldn't figure out what happened, but we sent it into Stewart, and got our money back. About a year later, I went to what was then known as NSCA, now known as CEDIA, and asked Stewart what happened to the amp. I talked to a tech, and he said that they had a production problem, that the insulators behind the 300 volt switching transistors ended up leaking to ground over time, and that they had more than one amp do the same thing, but ours was the best example of 'it done blowed up real good'.

Too bad we didn't have digital cameras back then, that would have been a great picture!

[Curt Palme]

I'll see if I still have the board. It's an H output board from a 3600. It caught fire, and I guess it smoldered long enough just not to blow whatever fuse would protect it. It cooked the board bigtime. I saved it for the capacitors, there were actually few parts blown on the board, but enough to make it a Curt 'classic'.

Now, to be fair, I've had my own personal Barco retro 808 do the same thing, a glycol leak into the convergence board multipin connector smoked it and blew a hole in the board as well, but I repaired that one.

I don't think an NEC has blown a board up, but I do have a motherboard from a 9500 Ultra that also fried a few traces making it beyond repair. That was a glycol leak as well.

The best one ever though was non CRT related. We sold a first generation Stewart power amplifier into McDonald's corporate boardroom, I think in 1992 or so. It used a switching power supply, much like the Marquee that was auto switching from 100 to 240 volts. Very lightweight, about 20 lbs or so, 100 watts per channel. We got a call about a week after we put it in: 'Umm, there's a really bad burning smell in the boardroom, and we think it's coming from the sound system'.

We get there, and the boardroom opens up into a big atrium where reception is. 20' ceilings, etc. The whole damn place smells of burnt silicone.

The Stewart amp had smoked, and as with the Ampro, didn't blow the fuse. We were reallly embarassed of course, pulled the amp and put another one in. IN the shop, I opened the amp, and it was divided into 2 sections, the switching supply and the audio amp section, separated by metal shields due to the noise that the switching supplies put out. I swear, it looked like a bomb had gone off in the switching supply section. I mean, I opened the amp, and a puff of burnt silicone/fibreglass floated out of the amp. Everything was black and charred. I couldn't figure out what happened, but we sent it into Stewart, and got our money back. About a year later, I went to what was then known as NSCA, now known as CEDIA, and asked Stewart what happened to the amp. I talked to a tech, and he said that they had a production problem, that the insulators behind the 300 volt switching transistors ended up leaking to ground over time, and that they had more than one amp do the same thing, but ours was the best example of 'it done blowed up real good'.

Too bad we didn't have digital cameras back then, that would have been a great picture!

[macgyver655]

Ok. so it was more of a busting Chips chops kinda a post.

I've also seen my share of crisp and fried parts and boards in tv's, amps, rptv's and such. Use to get a lot after lightening storms. Business always tripled after a good electrical storm. Traces burnt and curled up , some needing 20 to 40 jumper wires to become functional again.

[Curt Palme]

Yeah, more or less.

Yep, I always loved the 'why did the TV smoke, it wasn't ON' comments.

[Curt Palme]

Yeah, more or less.

Yep, I always loved the 'why did the TV smoke, it wasn't ON' comments.

[stefuel]

[Curt Palme]

No, I've always liked them. The POS Spellman HV supplies are as prone to failures as the ones in Marquees.

The most reliable HV section by far is the NEC ones. Problem is, NECs have all sorts of other issues to make up for it.

[Curt Palme]

No, I've always liked them. The POS Spellman HV supplies are as prone to failures as the ones in Marquees.

The most reliable HV section by far is the NEC ones. Problem is, NECs have all sorts of other issues to make up for it.

[draganm]

[tse]

If I remember right those are 62 ohm 5% (61.9 ohm if 1%) 1/2W jobs that are used as fuses/resistors. They are flameproof so don't burn up the PCB if they are overloaded.

These are the ones:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=5033ED61R90F12AF5-ND

Search for sfr16s or 5033ed type.

Scott

[Curt Palme]

[Curt Palme]

[macgyver655]

[draganm]