SFdeluxe with no tremolo

[pontiacpete]

I've tried just about everything except changing out the optocoupler and still no trem. The light flashes and slows and speeds up when turning the speed pot. Changed all the caps in trem circuit and checked all resistors and tried new pots, new tube,, cleaned socket.
pins
1. 270 to 325v
2. 1.3 to -1.v
3. 1.2 to 2.4v

6. 280 to 360v
7. 0
8. 17v

I'm at a lost at the moment,
Since I'm not an expert I even checked it against a working SFD and still can't locate the problem...mmm
Does anyone feel like helping me out? It'd be greatly appreciated.
Thanks
pete

[Enzo]

So the light bulb half works. You done any checks on the photocell side? The whole point of the flashing bulb is to throw light ona photocell, which then changes its resistance.

[pontiacpete]

I checked the resistance between the legs of the photo cell and got 10meg or so on the end facing the tubes, the side that gets HV. THe other end I measured 30K. I don't know how to test the cell. ??,, THe light does flash like a normal working one, though.

[jrfrond]

You "shotgunned" the trem circuit repair, and neglected to replace the #1 culprit, while replacing less likely suspects. Get yourself a new "bug".

[pontiacpete]

Thanks, that was it. I replaced it with one from the good deluxe and sure enough that was the problem.
Is there a way testing the opto' so I don't end up pulling apart a circuit again? What do shops do? Do they put a new one in right off and then go from there?

[Enzo]

Once the amp is open in front of me and I see the bulb flashing and no trem effect, my first reaction is to try a new bug.

It takes less than a minute to heat the four leg's solder joints and pull them up. I like to prep the holes for the new part. Another minute, and a third minute to solder a new one in. Really, I am not bragging, it just isn;t a lot of work to solder four wires.

If that cures it, I can move on. if for some reason that was not what it needed, I can reinstall the original part in another three minutes.

When someone is paying me a dollar a minute or more, how much time should I use trying to test things? Same reason I never use a tube tester, I just sub a new tube into the amp and see if that was the trouble.

But the bulb flashing is half the battle. Stick your ohm meter on the photocell leads and see if the resistance is moving up and down with the flashing? The photocell leads are the two with no high DC voltage on them. This is one area where an analog meter may be easier to interpret.

[pontiacpete]

Great! measure the resistance with a VTVM on the low voltage side or just swap out first.
thank you very much, Enzo.