Asteroid/Express 911

[moj067]

I've attempted an express to Asteroid conversion.
The volume when dimed sounds like 1/2 wattage, not flame thrower loud like in it's previous life.
Keep in mind this amp has a 5.2/6.6k switch and a tube/ss. recto switch.
Thought I could have a flexible amp.
pre-amp was done per tsl's conversion.
Changed out everything I could to make this work, now stumped.
Thinking the problem might be in the power section somewhere.
Hopefully some of you eagle eyes can point me to the right direction.
Many thanks in advance for any help.
-Joseph

[moj067]

I'm thinking now that the .022cap and 220k res. to 1m res. in P.I. are the gate keepers here. I know I'm responding to my own post, but keeping in spirit of this forum I'm just playing w/ this and documenting efforts for the benefit of others. Anyway still having fun w/ this problem child of mine.
-joseph

[Fischerman]

It's difficult to see where all the wires are going but your tone stack doesn't appear to be wired correctly. Look at one of the layouts and verify your tonestack. There is also what appears to be a stray blue wire that's not connected to anything near the V2 socket. I can't see exactly what's going on around your 'Fast/Gradual' switch but I would triple check that.

You could also put a signal into the amp and then measure the AC voltage at different points to isolate where you're losing all your signal. If you have a 100mVac signal at the input you should have in the ballpark of ~4Vac on the first plate. With all tone controls on '5' and volume full-up you should get in the ballpark of 2Vac on the second stage grid...keep probing each grid and plate until you find where you're losing all your signal.

Also; measure all power supply, plate/cathode voltages throughout the amp (this should be one of the first things you do when troubleshooting).

Also, one last note: you should always try to keep your treble wire as short as possible and away from everything else (except maybe the chassis). Treble wires are very susceptible to oscillations and other funkiness. It looks like your treble wire is doing a loop down there.

[moj067]

Thanks. the blue wire is a remnant from prior express wiring scheme.
The tone stack is wired per the Asteroid layout with change outs of the Treb. and Bass pots to 250k as well.
I'll get some signal in there and check it out.
Thanks a bunch for your input.
-joseph

[dobbhill]

I might try to lose the master volume until I got it sorted out...Just a suggestion.
D

[dobbhill]

What's the blue wire next to V2 do? The one that's not connected to anything? Where is the red wire on pin 1 of V2 connected?
HTH,
D

[moj067]

The 1st pin of V2 is connected to where the Sozo .02 and 100k resistor connect on the top of the board. Would another pict. of the other side of the board help? Thanks for the inquiry.
-joseph

[Fischerman]

I might try to lose the master volume until I got it sorted out...Just a suggestion.

That looks more like a 'Cut' control...and appears correct.

Upon further look...the tone stack may be right...I was seeing a few wires incorrectly there.

Try measuring all dc voltages at idle and then putting signal through it and measuring the AC voltages throughout...that will likely point you right at it.

[jurgen]

I'd check the voltage at the first filter cap

it's lttle hard to see but if thats Nik's PT then

the rectifier wiring looks suspicious

[moj067]

I've checked the voltages at the typical filter nodes and came up w/
400v
365v
329v
312v
I have found a problem w/ my preamp heater voltages.
They are all at around 1.8v not the healthy 6-7v. they should be.
Where do I look next?
My power tubes are at around 30ma using a bias probe.
Thanks for the input gentlemen.
-Joseph

[LeftyStrat]

I've checked the voltages at the typical filter nodes and came up w/
400v
365v
329v
312v
I have found a problem w/ my preamp heater voltages.
They are all at around 1.8v not the healthy 6-7v. they should be.
Where do I look next?
My power tubes are at around 30ma using a bias probe.
Thanks for the input gentlemen.
-Joseph

It could just be the photo, but make sure pin 6 and pin 5 on the first preamp tube aren't touching. Also, make sure you're measuring AC voltage and not DC on your meter.

Then just "divide and conquer". Unsolder the heater wires from the PT and make sure you're getting 6.3 VAC from the PT. Then solder them back into the first power tube without the rest of the chain connected and make sure you still have the correct voltage. Go down the line adding in one tube at a time until you find the problem.

Is there a center tap on the PT for the heaters? I couldn't see from the pics.