Soldano slo 25

[JMMP]

Preamp tubes are super hot. Heater is dc, reading 13 volts on pin 5, nothing on 4, and nothing between 5 and 9. What the hell is going on? Contacted the email Soldano support lists but no response

Thanks in advance

[Helmholtz]

Heater voltage is always measured between heater pins - not to ground.
13VDC between pin 4 and pin 5 would be ok.

Pull the tube and measure resistances between heater pins. Pin 9 is the filament center tap.

Please post schematic.

[JMMP]

Thank you, will check that again when I get in. Tubes are running as hot as the power tubes, and hisses more than it should, both channels. Will get back to it soon.

[TomCarlos]

Just curious.... Is this amp an 'SLO 25"? I can find the SLO 30 and Hot Rod 25, but no "SLO 25." Maybe that would help us find the correct schematic. Thanks.

[g1]

I guess you mean super hot compared to 6.3V heaters? The heaters can be wired parallel 6.3V or series 12.6V, this one will have them in series, so pretty close to the 12.6V spec. (if you confirm 13V between pins 4 & 5)

[JMMP]

It's a Hot Rod 25, my apologies. Yes getting 13.6 across 4 and 5. Can't find a schematic for this one anywhere, amp hisses on both channels if any gain is up. Anyone know the tube layout, want to try a pair of tung sol in the early stages.

[JMMP]

Swapped 2 tubes out, significantly better. Thank you guys for all your help!