I have new glasses since a week. Is it because of that or am I right in saying that in all the schematics that can be found on the net and even from the distributor a page is missing.
Here a link to the schematic:
www.valvetronix.net/docs/AD120VT_Service_Manual_Complete.pdf
The page in question is the one that's named MAIN PCB in the block diagram.
I have the "complete" service manual attached.
The problem is some where on that board but without a schematic...
If some one of you guys have that particular page, can you forward it in way or the other?
I'll be very happy as well the customer.
And to avoid the inevitable question; What's wrong with the amp?
One speaker has a very low output. About 16dB.
The speakers are OK. The power amp is OK. The circuitry around V1 and V2 is OK.
On connector CON1 there is a lower signal level then on CON2.
So it's obvious a problem on the MAIN PCB and the need for the schematic of that part.
Thank you for your help.
Here a link to the schematic:
www.valvetronix.net/docs/AD120VT_Service_Manual_Complete.pdf
The page in question is the one that's named MAIN PCB in the block diagram.
I have the "complete" service manual attached.
The problem is some where on that board but without a schematic...
If some one of you guys have that particular page, can you forward it in way or the other?
I'll be very happy as well the customer.
And to avoid the inevitable question; What's wrong with the amp?
One speaker has a very low output. About 16dB.
The speakers are OK. The power amp is OK. The circuitry around V1 and V2 is OK.
On connector CON1 there is a lower signal level then on CON2.
So it's obvious a problem on the MAIN PCB and the need for the schematic of that part.
Thank you for your help.
It´s ALL there, black on white.
The circuit is very complex, specially what lives on the main board, so each functional block has a page devoted to it or you would need an open tabloid newspaper double page to display it properly.
As a guide of what goes where, check for interconnections shown on the block diagram, such as , to get a simple one:
Input jacks go through connector CN1 into the codec front end on "Main PCB Block Diagram" ... which is the Main PCB of course, and which is shown with more detail, actual circuit and parts values on the page labelled "Analog-In" .... and so on.
To follow signal path follow the connectors, they are joined by not shown ribbon cable.
Not shown for good reason, they would clutter the drawing immensly, so to follow signal, voltages, ground, etc. you refer to connector name and pin number.
That said, these are very complex amps, as I call them "computers with a 100W Audio Board driving Guitar speakers", and well beyond troubleshooting abilities of "normal" Techs (me included), unless the problem lies in the fully Analog/conventional section, such as a blown Power Amp or defective Power Supply.
Or maybe bad jacks/switches/pots/encoders (which are just a special type of switch) , but nothing beyond.
I bet "VOX" (actually Korg) themselves do NOT repair these amps at component level, just one hour Tech Bench cost is more han parts and PCB are worth so they plain replace the defective module and call it a day.
I bet when your Computer mainboard, Audio or Video Board malfunction you don´t grab the Digital Analyzer or wideband triggered multichannel scope and start looking at waveforms and clock pulses, do you?
Main point: unless there is a "mechanical" problem involved, or a supply/power amp failure, send it back to customer and let him handle VOX/Korg repair at an Authorized Center, at least because they can get parts which you won´t.
The circuit is very complex, specially what lives on the main board, so each functional block has a page devoted to it or you would need an open tabloid newspaper double page to display it properly.
As a guide of what goes where, check for interconnections shown on the block diagram, such as , to get a simple one:
Input jacks go through connector CN1 into the codec front end on "Main PCB Block Diagram" ... which is the Main PCB of course, and which is shown with more detail, actual circuit and parts values on the page labelled "Analog-In" .... and so on.
To follow signal path follow the connectors, they are joined by not shown ribbon cable.
Not shown for good reason, they would clutter the drawing immensly, so to follow signal, voltages, ground, etc. you refer to connector name and pin number.
That said, these are very complex amps, as I call them "computers with a 100W Audio Board driving Guitar speakers", and well beyond troubleshooting abilities of "normal" Techs (me included), unless the problem lies in the fully Analog/conventional section, such as a blown Power Amp or defective Power Supply.
Or maybe bad jacks/switches/pots/encoders (which are just a special type of switch) , but nothing beyond.
I bet "VOX" (actually Korg) themselves do NOT repair these amps at component level, just one hour Tech Bench cost is more han parts and PCB are worth so they plain replace the defective module and call it a day.
I bet when your Computer mainboard, Audio or Video Board malfunction you don´t grab the Digital Analyzer or wideband triggered multichannel scope and start looking at waveforms and clock pulses, do you?
Main point: unless there is a "mechanical" problem involved, or a supply/power amp failure, send it back to customer and let him handle VOX/Korg repair at an Authorized Center, at least because they can get parts which you won´t.
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I have repaired a few and IC8 can give trouble because it is not driven properly or the supplies are low. If IC8/3 does not switch it will switch one amp into class A which gives lower gain.
Maybe wrong but the whole amp is on your diagramme. If you are not trained by the manufacturer, you may well never figure it out!
Maybe wrong but the whole amp is on your diagramme. If you are not trained by the manufacturer, you may well never figure it out!
It must have been thee new glasses that's for sure. It make's me see wider (they are multifocal types) then the previous one. I still have to get used at the clearer (?) view of them.
Any way, I wasn't 100% lately and still my back is troubling me. This probably made me so tired to have a close look at the schematic. A schematic that could have been drawn a bit better but hey, what do you expect from VOX.
As said by JonSnell, all is there.
Early next week I have a further look at it.
I keep you informed.
cheers
Any way, I wasn't 100% lately and still my back is troubling me. This probably made me so tired to have a close look at the schematic. A schematic that could have been drawn a bit better but hey, what do you expect from VOX.
As said by JonSnell, all is there.
Early next week I have a further look at it.
I keep you informed.
cheers
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