Channel Vision CVT-2/8 PIAII cable amp

[bluto]

My whole house video amp has conked out. It works for a while then quits. When it does the LED goes out. So I opened it up to see what I can see. There are three 'STONE' brand 'lytics (2x 100uf and 1x 10uf). They are a bad brand but read ok with a capacitance meter. I would just shotgun some new ones but It seems this board won't come out without un-soldering all of the connectors (I removed all the screws but it wasn't budging.


So I looked at it some more and the 4 pin SMD transistor looking thing with the markings "DL 28" looked a little suspect. I thought maybe it was just a bad solder joint so I touched it up and the amp came back to life. So I left it plugged in on the bench but when I came back after a while the LED was out again. So in looking at it some more, it looks like it got hot and touching it confirms this suspicion. It has a steady 12v going into it but the output is fluctuating. When it is working, 9v is coming out and feeding down to the LED and the row of 5 more SMD transistors above the two 'lytics.

So this seems like it could still be a easy fix if I could find a replacement for that flaky transistor. I have some chipquik so I think I could pull off replacing it.

Any thoughts? How would I track down an equivalent part on digikey?

[bluto]

Re: Channel Vision CVT-2/8 PIAII cable amp

Ok so if the failed part is just acting as a voltage regulator to take 12v down to 9v... Is there any reason why I couldn't just replace it with something like this:

http://www.digikey.com/product-detai...711-ND/1828604

A 12v to 9v regulator. I seems like it would fit in there without too much trouble.

[selldoor]

Re: Channel Vision CVT-2/8 PIAII cable amp

Are you sure it says DL 28 The tables I have looked at dont have a DL
and the 28 could be ZB Can you try cleaning it up and checking.

[bluto]

Re: Channel Vision CVT-2/8 PIAII cable amp

Its definitely "DL 28" It has "FF" inside the small circle in the middle. It is a SOT-89 package: 4.5mm x 2.5mm x 1.5mm. Looking at it with the tab on top it matches with the pin-out of another transistor data sheet where pin 1 was gate, pin 2 was drain, and pin 3 was source.

[bluto]

Re: Channel Vision CVT-2/8 PIAII cable amp

I went and looked at the one installed at my parents house. It is identical except a few years newer. It has Jackon caps instead of STONE. The device in question on that one is labeled "DL 5Y" if that helps any. I really want to fix this sucker. Any ideas on how to narrow down the search for this part?

[ReverendJones]

Re: Channel Vision CVT-2/8 PIAII cable amp

Hello Bluto.
The DL part code looks up as a 2SB798, a PNP transistor (The 28 & 5Y are date codes). The transistor driving it, L6, looks up as a 2SC1623A, a NPN transistor.
If the DL/2SB798 is heating up, there may also be a short somewhere on the output.

2SB798 datasheet

[bluto]

Re: Channel Vision CVT-2/8 PIAII cable amp

Thanks Reverend! It looks like it is an obsolete part but still available in a few places.