CurtPalme.com Home Theater Forum

[Anderssh]

Hey Guys!

I bought a Barco 800 from Curt two-three years ago or so, and I've just recently encountered a problem I was hoping you could help me with before I bother him with it.

The FET on the red Output Board had been getting progressively worse for some time (eventually causing diagonal lines), so I decided to change it. A kinda hard-to-find component, at least over here, but soldering and installing was no problem when finally I received it. Everything worked flawlessly, and the red picture was even greatly improved in sharpness compared to pre-FET failure.

After watching three movies on separate occasions though, half way through the fourth there was an audible "POP" and the projector blacked out for a few seconds. When the picture returned, the red tube was dead. I assumed I had messed up the soldering or hadn't reattached the transistor to the heat sink good enough - but when I checked under the hood, I noticed that I had put the green board in place of the red and vice versa. Nothing wrong with the recently repaired board.

Changing the output boards confirms that's where the fault is. However, as far as I can recall, all three output boards are identical and should be interchangeable, so putting one in the place of another shouldn't cause problems. Before I change another FET I thought I'd consult you first - is this just an unlikely coincidence or do you think there might be something before the output board that could be causing it? I'm not sure it's the FET that's the problem, and I don't have any measuring devices other than a multimeter to check.

I should also mention I did a re-calibration of the G2 and focus pots after changing the transistor.

[kal]

The boards are completely interchangeable from what I remember. I've done it in the past to check something with my BG800 when I had the same problem (ended up replacing all three 2SK511's on the neckboards).

Check the service manual if you're not sure (it's on the site here). If there's only one neckboard part # then you're 100% sure they're the same.

Kal

[kal]

The boards are completely interchangeable from what I remember. I've done it in the past to check something with my BG800 when I had the same problem (ended up replacing all three 2SK511's on the neckboards).

Check the service manual if you're not sure (it's on the site here). If there's only one neckboard part # then you're 100% sure they're the same.

Kal

[Anderssh]

Yeah, the service manual confirms the same part numbers, 76 1750

I just find it odd that the now broken board would go so soon after the one before it. I'll go replace it in the morning to see if it breaks again and send Curt an email if no-one can think of something else that might cause this

[Curt Palme]

It's possible that an intermittent short in the tube is blowing/damaging the FETs.

Yes, those transistors are REALLY hard to find now, I am out of stock, and the last place that I could find that had them wanted an order of 100 in order to process.

I have about 20 rebuilt boards and with low demand for these now (I've only had one pub blow a second transistor, and they put 20,000 hours on the chassis(!)), I don't know if I need to buy any more at this point.

[Curt Palme]

It's possible that an intermittent short in the tube is blowing/damaging the FETs.

Yes, those transistors are REALLY hard to find now, I am out of stock, and the last place that I could find that had them wanted an order of 100 in order to process.

I have about 20 rebuilt boards and with low demand for these now (I've only had one pub blow a second transistor, and they put 20,000 hours on the chassis(!)), I don't know if I need to buy any more at this point.

[Anderssh]

[Curt Palme]

Red tubes are cheap, but I'd change the FET one more time to see what happens. I've recently had one bad one in my batch of 100 that I bought 3 years ago.,

[Curt Palme]

Red tubes are cheap, but I'd change the FET one more time to see what happens. I've recently had one bad one in my batch of 100 that I bought 3 years ago.,

[BurnerX]

[Curt Palme]

Well that's true, but as I stated above, I started changing them out on every 800 I've sold since about 2002 when I found out about this issue, and the only repeat failure I had was in a strip bar where they run them 14 hours a day. I figure they put 20,000 hours on the chassis since I sold them the set in 2003 or so.

[Curt Palme]

Well that's true, but as I stated above, I started changing them out on every 800 I've sold since about 2002 when I found out about this issue, and the only repeat failure I had was in a strip bar where they run them 14 hours a day. I figure they put 20,000 hours on the chassis since I sold them the set in 2003 or so.

[Anderssh]

I changed the other FET on Saturday, and so far it's working again. However, there is a spot burn that wasn't there before so I guess I should look around for a new red tube anyway. Or actually, I think I will take this as a sign to start saving up for an upgrade.

[BurnerX]

[Curt Palme]

Well, if someone tweaked those gain controls on the board, the FET can run red hot. I'm sure many customers of mine have run well over 1000 hours on their sets with no issues. I'll bet your blue output board runs a lot hotter than the other two..

[Curt Palme]

Well, if someone tweaked those gain controls on the board, the FET can run red hot. I'm sure many customers of mine have run well over 1000 hours on their sets with no issues. I'll bet your blue output board runs a lot hotter than the other two..