Anyone Recognize This Vintage Davoli?

[dankinzelman]

Hi everyone,

I'm trying to figure out what's wrong with this old Davoli amp. After replacing an output valve with an internal short which was blowing fuses it still doesn't produce nearly the volume I'd expect and breaks up very early. So far I have been unable to locate a schematic which matches what I see in the amp itself.
Anyone know anything about it?

[Platefire]

Never Heard of that Brand?

Need to do some basic trouble shooting at this point. The most basic is replace the other power tube with a known good tube to see if makes a difference. Same with the pre-amp tubes. The shorted power tube could have taken out something else while it was blowing fuses. A visual check of the circuit for any burnt parts would be in order.  I would be inclined to pull all the tubes(take the load off) and check voltages at all the major points of the circuit to see if there is any drop outs of voltage. Cleaning the pots and tube sockets with contact cleaner can also make a big difference if the amp has been out of use for a while. Platefire   

Doug does have some Davoli schematics but I don't see one labeled "C3"https://el34world.com/charts/Schematics/files/Davoli_krundaal/Davoli_krundaal_Schematics.htm

[dankinzelman]

Thanks Platefire,

yes, Davoli is a well known brand here (I'm based in Italy).

I should have clarified: both output tubes have been replaced by a matched pair of new tubes. The problems I'm described are apparent with the new tubes. The B+ for the output tubes seems to be frighteningly high on this amp (around 700V if I recall correctly!). The main smoothing caps have been replaced by two 400V caps in parallel.

In October I should have some time to sit and fuss with it, I'll update as I dig through it.

[kagliostro]

Ciao Dankinzelman

I think that the most part of the Davoli Krundaal schematics that you can find on Doug's database

were sent to him by me

I dont' know that particoular amp (the Davoli C3) and I'm asking to other friends (on this side of the pond) if they have news about

The Power section seems to be an UP60 but about the preamp section, at till know, I know nothing

It will be nice to have the schematic of that (whole) amp, if you are able to retroengeener the circuit I can draw the schematic in FidocadJ

Franco

EDIT: A friend had that schematic and sent it to me so I can share it

The B+ for the output tubes seems to be frighteningly high on this amp (around 700V if I recall correctly!).

New EL34 suffer a lot with this high voltages, they are not the same tube of the OLD STOCK, sometimes ago a friend told me he had immediately problems with the new version of the tube and one (or bot ?  don't remember well) fried after few time


I don't have an under hand solution to that problem (OK you can find some OLD STOCK tube), I think you can try to lower G2 voltage and see what happens (if tubes are still OK, pay attention they must NOT redplate)


May be you can try with KT77 (or 6CA7 if you find it)

[dankinzelman]

Thank you Kagliostro!

I'll see where this gets me.

Dan

[kagliostro]

Ciao Dan

Puoi trovarmi anche su DIYitalia (http://www.diyitalia.eu)

Franco