Madison Divinity 12 Tube Amplifier Combo

[Dave_D]

Picked this Amp up for a song, had the usual issue with heater system caps and needed new tubes. Replaced all tubes and repaired caps. All tubes are firing and a quick run of the pin voltages show that everything is in normal operating range. this issue is there is very little volume. Ive performed the standard trouble shooting, effects loop, tube position swap, etc. the performance (or lack of it) has remained consistent.

Has anyone else run into this issue with this brand or have any tips on where else to look?

[Platefire]

Not sure what you mean by heater system caps? Do you mean power supply caps?

Other basic things to check:

1-test with a different speaker
2-Try different guitar and cord
3-Did you check plate voltages to power tubes
4-usually with problems like this, a chop stick probe of circuit with amp live is in order. This is dangerous if you not familiar with dealing with high DC voltages, so take all precautions to protect yourself. A high voltage DC shock can kill you. When your probing with a chop stick and touch something and the volume picks up, then that might be your problem.

Platefire

[Dave_D]

it has a funky DC heater circuit, separate rectifier and 7 capacitors that provide a DC voltage (to reduce hum?)

The clean channel has moderate volume (no where near what 2 EL34's produce) all the dirty channels are barely audible.

I did plug it in to my Hiwatt 4 -12 cab and the sound was no different.

Plate voltages on the power tubes were VDC

[eleventeen]

Could be biased massively cold...could be somehow lacking adequate drive to the output tubes...bad output tranny...open capacitor in the signal chain....bad solder joint....open ribbon cable, if present... Gotta dig deeper.

[silverfox]

A search for a schematic reveals difficulty in obtaining one. I don't know if you have one or not. If not, this may be a copy of a Marshall DSL. That sch is readily available, you might get one for troubleshooting purposes. There are mixed reviews for the amp, (good-bad) but if it is a DSL copy, lots of Mods and other info out there. Simple search turned up DSL sch's.


I also ran across a description of a similar problem that was intermittent and the suggested path was to check the input jacks and tube sockets. Sounds like you already did that.


Silverfox.

[Dave_D]

Thanks to all.

I did a full voltage chart and all tubes are with in normal operating voltages when compared with averages in 50 Watt EL34 circuits.

I tried using 2 different speaker cabs and received identical results, weak volume in the clean channel and next to no volume in the other channel.

The pots tested fine, unfortunately the use a mini pot with a bracket and it required taking off the entire pre-amp board to test, both are fine.

I probed with the chop stick while the amp was live and still had no change in performance.

I don't think it is the out put tranny as it would preform equally poor in either channel and not louder in the clean one as it does now.

i ran the input jacks as well as the effects loot and foot switch jacks and all were ok.

Exploring the caps now, hoping that i find something a miss there.

again thanks to all.

[Dave_D]

i decided to try the amp with the pre amp board hanging loose.

BOOM

loud and clean and the Edge channel working as well. Bad ground or a weak ribbon must be the issue, either are easily overcome.

Again thanks, much thanks to all.

[Platefire]

Great! Glad you found it.