Deaf Row!

[walpurgis]

Bugger! My SM-70 Pro power amp has died. No noises, no funny smells, mains fuse is OK. Just no light on the front, no sound and cold heat sinks. Power supply I reckon. Hope it's not the transformer. I'll open it and have a look tomorrow.

Got the top off my SM-70 Pro.



Transformer looks fine and no funny smells. The fuses on the power input side to the two halves of the PCB are fine. The obvious suspects to me are the pair of bridge rectifiers bolted above the transformer. I checked the rectifier spec, they are 6 amp, is that on the low side for a hot running Class A job? The amp has been fine for years though. I'll bung a meter across them, if one is shorting inside, I should have the culprit. I'd replace the pair though. I suppose I should measure the transformer too. I don't know what the values should be for the primary and dual secondaries. I guess continuity would be a start.

[struth]

i guess somewhere up to about 100 ohm and no leakage between the 2.

[struth]

caps may need tested if you cant find anything... also the cable i suppose

[Firebottle]

6A sounds fine to me Geoff, as there is one per channel.

Primary of the Tx is probably 10-20 ohms, toroidal figures are pretty low. Secondaries will be a fraction of an ohm I guess.

Good luck

[walpurgis]

Wot's this 'ere then?



Tucked under my Monarchy Audio SM-70 and next to my EL34 monos. Looks like a flippin' Quad 306. How did something like that end up in my system?

[southall-1998]

Interesting! How are you finding the 306, Geoff?

S.

[dantheman91]

Seems like we have converted geoff to a Quad fanboy....

I'm sure you will like the 306........

[struth]

Wot's this 'ere then?



Tucked under my Monarchy Audio SM-70 and next to my EL34 monos. Looks like a flippin' Quad 306. How did something like that end up in my system?

Messy... get that tidied lol

[walpurgis]

Interesting! How are you finding the 306, Geoff?

S.

Not bad at all Shane. Input sensitivity is high. I may bung a stepped attenuator passive together for use here. Got all the bits.

As you'd expect, it sounds different to the valve and SS Class A stuff. It's a pretty benign sound, no nasties whatsoever. The Tannoys seem to like it.

Nice 3D midrange, deep bass (if not quite as tight as the Monarchy, but not bad). Top is clean. I'd say it's got 95% of the lucidity I'm used to.

The sound seems to have been improving slowly as it's been in use. Plenty of punch too.

Never tried a 306 in my system before. I've heard them elsewhere sounding pleasant a few times. That's why I thought I'd give one a whirl.

Quite pleased with this actually. In sound terms, it's an absolute bargain for the money these go for.

[walpurgis]

Messy... get that tidied lol

Damn cheek!!