vox valvetronics head

[Gunn_Slinger]

hey guys
havent gotton into tearing the head apart yet.
i read about old amps being affected by house voltage over 110....mine is 123.
any chance this amp/computer doesnt like the higher voltage?
i also read that a weber browner is a good voltage reducer.
any thoughts would be good......im lazy till it gets cold here in virginia and runs me off the golf course...lol
thanks
Clay

[Enzo]

That's fine when you talk about amps from the 1950s, but this is not an old amp. Many are still under warranty even. other than teh power amp which doesn't care, all the inner voltages are regulated anyway. Mains voltage is not an issue.

[Robert M. Martinelli]

That's fine when you talk about amps from the 1950s, but this is not an old amp. Many are still under warranty even. other than teh power amp which doesn't care, all the inner voltages are regulated anyway. Mains voltage is not an issue.

Hi Enzo!
How are you doin'?
Well, I would say mains voltage is not an issue if it falls within reasonable limits, otherwise it could stress the transformers and voltage regulators....
( Here in Italy the Electric Co. wise guys, to lower the substations' number, used to start with a very high voltage, and run the same line for miles, this way the "poor guys" close to the substation got 260 VAC instead of 220, while the guys at the end of the line got 200 VAC, this way the Electric Co. destroyed a good number of TV sets and VCRs, and later lost a lot of money in courts ).

In this case 13V more represent some 11 percent, this means 23 percent more power to be dissipated on the PT and regulators, so i would expect them at least to run at a higher temp, which can decrease life expectancy....

OTH it is true that other amps are more forgiving than the Valvetronixes, whose reliability record is unfortunately very poor, ( such a pity because they' re otherwise very versatile and good sounding amps ), so generally a 10-15 percent higher mains voltage is not an issue.

How I wish Vox was still building their amps in the UK! Imagine a good idea, ( like the Valvetronix is ), turned into a versatile, sturdy, rugged, well built amp with no reliability issues whatsoever - a guitar player's dream! Sixteen amps in one plus effects, without having to worry about a thing! - Stop dreaming, Bob!

[Enzo]

Yes, a rise of 13v in the mains would mean more dissipation in the unit, but the point that was raised was comparing the old 110VAC mains for 50 years ago with the 120v mains of today - 123v being a common level for it. The Valvetronix was never designed as a 110v amp, so the 110/123 issue is moot. The difference discussion arises when someone looks at schematics for a 1950s era amp and finds all the voltages are higher because the mains are now higher. His house has 123v on the mains, and the amp is designed as a 120v amp, so that is well within the range of proper voltage.

Obviously if the local mains are unreliable or not consistent, that is an issue to pay attention to, but it is a separate issue from the one brought up.

[Gunn_Slinger]

thanks guys
so power is ok
latest tests : went line out of the vox to the receive of a borrowed marshall head.....the signal was pretty clean, but i did notice that the amp emulations were not as prononced....more on that
Then i went from the marshall line out to the receive of the vox....surprisingly
((( spell check!!!...lol ) the signal was pretty clear.
Started read manual about the vox using the 12ax7 into a dummy load as a power amp emulation along with the pre amp emulation.
Sounds like the line out on the vox bypasses the dummy power amp and the receive in also bypasses it?
I cant find the schzo on it ( only the newer 50 and 100 watt are on their website )
Could the dummy power amp be the problem?
thanks again
Clay

[Enzo]

SIgh...

Reread the last paragraph in post #7 Gunn.

[mr.jetski]

gunslinger vox and enzo, hi all,

if that thing is at all like a peavey tubefex the noise gate threshold is set to low. I found that the hard way!

[Enzo]

There you go, a different direction to try. From your description it sounded to me like a stuck low bit, first impression anyway, but certainly other avenues are worth exploring. I am familiar with fixing them, but I don't know about their features. I'd be surprised if it didn;t have a gate.

[Gunn_Slinger]

thanks guys
it has an adjustable noise gate which ive tried in many positions ....it works to take away noise at idle but has no effect on the signal noise.
enzo, i read post #7 and i dont know much about the parts you talk about.
i dont know how the 12ax7 power amp into a dummy load works, i built some tube amps in the 50's and havent done anything with amps till now ( becomming sorry i did...lol )...so im not sure to what you are referring.
just a note ,i put an mxr smart gate in the effects loop and it nakes the amp playable ( for now ). What do you think a shop would charge to work on this amp?
thanks for all the support
Clay

[Enzo]

I was referring to the last paragraph, wherein I mentioned that sending me an email would get the drawings in return.

I cant find the schzo on it

You'll have to find a shop willing and able to work on it, and then ask their rates.

[Gunn_Slinger]

thanks enzo
i emailed you .
where would i start looking for a stuck bit?
later
Clay

[Enzo]

REmember it is only my notion that is the problem.

I would be looking in the A/D-D/A areas first I guess.

[Gunn_Slinger]

hey enzo
got the sczho...thanks
was reading about the self test modes
do you know how to use it and how to read the output codes?
thanks
Clay

[Enzo]

You now have the same service manual that I do. All I know is from that.

I think I already posted this:

AD60 / AD120
Initialization

Switch the amp off.
Switch the amp on while holding down the UP and DOWN BANK buttons, and TUNER/CANCEL button. If you've done this correctly, a "P" will be flashing in the BANK Display.
Press the WRITE Button and watch the BANK and the four CHANNEL LEDs do a little dance as they indicate each one of the 32 programs being reset to its factory preset. Once they both stop "dancing," you're done. The amp will automatically enter Program Select Mode with Program 1 - 1, "Flying High," selected.

Mounting the "Amp Type" knob

The Amp Type knob is not keyed. So mounting it correctly requires knowing what Amp Type is currently selected. The factory setting for patch program 1 - 1 has an amp type of "UK Modern". The following procedure uses this fact combined with the Original Value LED to find the correct orientation for the knob.

Reset the unit.
With patch 1 - 1 selected, turn the Amp Type knob until the "Original Value" LED lights.
When this LED is lit, install the knob with the arrow pointing at "UK Modern".

[Gunn_Slinger]

yes you did post that and i did that
i was referring to page 12 of the sczho that talks about self test.
it outlines a number of tests but no info on what the readouts mean.
maybe voxrules or someone who has one of theses " monsters " has been thru this. as i said before my knowledge of amps is 50 yrs old and tubes only.
thanks again
Clay