Amp malfunction

[mikesayre]

Hi all-
I got an Acoustic model 134 guitar amp used, took it directly to the shop since the output seemed low, actually very low.
I got the tech the schematic, got the amp back and it acted the same; tech says all within spec. Asked about cap replacement, said he didn't do that unless it tested bad. I thought this was foolishness based on the filter cap probably being near or at the end of it's service life. Amp is probably mid-70s product.
Now I not only have the same low power output, but I get I think 60 hz hum upon power-up, channel and master volume controls set at 0 or turned up, resolves itself after 30-40 seconds. This symptom just started.
Any ideas beside take it to a diffferent tech?
Thx-
Mike S

[J M Fahey]

Did you test it before the Tech very eyes, to show him "low output" ?
That way either he sees there's a problem or he points you what you are doing wrong.
Otherwise the problem stays undefined.

[mikesayre]

Fair enough. I told him I thought it ought to be louder. This is based on over 40 years playing various amplifiers and comparing to to a similarly rated Acoustic model 123 I currently have.
This guy has been doing repairs for a shop I trust for upwards of two years, says he's been at it (both tube and ss) for about 30 years, I figured he'd know what a 100w amp should sound like; I think he mostly checked values against the schematic and called it good (not a bad approach).
"Should be louder" is perhaps nebulous, not sure how I should have languaged my problem for a different result.
Mike

[J M Fahey]

Power and volume are not the same.
He should measure power output (he probably did) and if in the ballpark of what's rated (maybe it claims 105 W RMS and it actually puts out 80/90W) then "he will find nothing wrong with it"
Which is right.
Charge the "missing 10/20W" to Marketing Dept. enthusiasm when writing the brochure, not to the Engineering Dept. which do the best within cost constraints.

When you wrote

the output seemed low, actually very low.

I understood you meant "like a broken pocket radio with dying batteries" or similar.
That would be a problem.
If you meant "I expect a 100W amp to sound louder" .... well .... perceived volume varies *a lot*  depending on many other factors, mainly speaker/cabinet/room/etc. not directly related to an *electronic*  malfunction.

[tubeAMP]

100W is a lot of power.  it should produce a lot of volume.  lot = lot :duh
not rocket science.  I would take it-back to the shop with the guitar that you play with it.  both you and the tech should listen at the same time and displace any suspicion  :grr