DIODES-IDENTITY

[Farthing]

Does anyone know the value-and purpose, of D5 and D6 Diodes on a guitar amp curcuit board?

[joecool85]

Does anyone know the value-and purpose, of D5 and D6 Diodes on a guitar amp curcuit board?

It depends entirely on what guitar amp it is.  D5 and D6 could be rectifying diodes in the power supply, input protection diodes or even clipping (overdrive) diodes on the tail end of a preamp etc.

[Enzo]

I could be wrong, Farthing, but it seems maybe you don't understand what part numbers mean.  Most schematics number the parts.  There can be hundreds of resistors in an amplifier, and we number tham so we can all know which one we mean.  We can't just say "that 1000 ohm resistor," because there could be twenty 1000 ohm resistors.  SO we number them.  Resistors we usually start the number with R for resistor..  SO R1, R2, R3, etc.

The same goes for other kinds of parts.  C for capacitor, D for diode, Q for transistor, K for relay, and so on.  SOme schematic drawers use CR for diode instead of D.  They will use either D or CR, but not both on the same drawing.

So D5 and D6 simply mean the fifth and sixth diodes on the schematic.  SOme companies start counting them at upper left and more or less go across the drawing assigning numbers.  Other companies tend to number their parts on the circuit board in some pattern, then putting the resulting numbers on the schematic.

IN any case ther is no standard.  There is no chart that tells you any diode numbered D5 will be a main rectifier or whatever.  The high voltage rectifier diode could be D1 in one amp and D47 in another.

And a lot of companies assign numbers in groups.  SO in an amplifier we might find all the power supply part number in the 100s, all the power amp section in the 200s and all the preamp section parts in the 300s, reverb parts in the 400s, tremolo parts in the 500s, or whatever.  So in that case R101, 102,103 would all be in the power supply, and R401, 402, 403 would be in the reverb circuit.  That doesn;t imply there are over 400 resistors, just a number sequence.

SO to answer your question, which we would happily do, we need to know what make and model amp you are talking about and have a schematic for it.  Then we can look and see what the diodes named D5 and D6 do.

[Farthing]

Thanks for the post. The amp in question is a Vox Cambridge 30 reverb. model no. V9130 made in 2005. I cant see the part numbers clearly on diodes D5&D6 without removal. One seems to say 00. I was advised to check these as there was a short in the system ( at voltage regulator) causing the transformer to get hot-although it did survive. As far as I am aware there is no schematic for this model available from the main agents certainly not in the UK.

[tonyharker]

Have you checked with Vox themselves. I recently got a circuit from them for a recently made amplifier.
If you quote the model and serial number to them they should help. Either phone their Technical Support Dept or use the on line email support form here < http://www.voxamps.com/contact/ >

Tony

[Enzo]

On that model D5 and D6 are plain old 1N4007 diodes.  They rectify the high voltage for the tube plates.  It isn't all that very high, because the filter caps are only rated 250v.   You should be able to determine if they are shorted without removing them.