Sano amplifiers?

[StevieRayVehkakoski]

Just bought one just like this:
http://www.talkbass.com/forum/showthread.php?t=556239

Except that mine has a huge square magnet on the 15" speaker and mine says on the control plate: "supersonic high fidelity amplifier" 

I guess this schematic should be close:
http://www.schematicheaven.com/bargainbin/sano_30-50w_30-50wr.pdf

Mine has the the 8417 output tubes replaced with 6550's? Are there any other subsitutes for the 8417's as at least I don't know of any guitar-amps that use 6550 output?

I'm also looking for some ideas how to get reverb on all the channels, right now the reverb is only on the "stereophonic" channel that has 4 triodes before the tone-stack and still it's the weakest of all 3 channels.. I guess I should check the amp carefully if it actually matches the schematic and also mine has the stereo-input modded to a normal plug-input and I haven't yet checked how it's connected.

[HotBluePlates]

Mine has the the 8417 output tubes replaced with 6550's? Are there any other subsitutes for the 8417's as at least I don't know of any guitar-amps that use 6550 output?

Because a single 8417 that's not used will cost you at least $55, where you could easily buy a pair of new 6550's for that price. And plenty of guitar amps used a 6550, they were just high-powered amps (or a wrong replacement for the EL34 in US Marshall amps).

I guess I should check the amp carefully if it actually matches the schematic and also mine has the stereo-input modded to a normal plug-input and I haven't yet checked how it's connected.

Yep. I can't tell you how to booger your amp, 'cause someone already got in there and boogered it! Find out what was already done first, because the schematic is useless if it doesn't match what you have to some degree.

[StevieRayVehkakoski]

Would a pair of 6L6GC's survive there? 500V at the plates and cathode-bias?

[HotBluePlates]

I wouldn't put 6L6's in that amp. Do you actually have a measured 500v in your power supply?

[PRR]

You do NOT-NOT-NOT want to run 8417 in a stage-amp. They were fragile in 1974 and unobtainium today. The few which survive should be left to the few super-sexed hi-fi amps which demand them.

The 6550 is notorious in the 2nd-generation Ampeg SVT. That was an OK amp.

They are also the preferred tube in the Ampeg VT-40 amps (they shipped with 7027 to save a buck, but the chassis says 7027/6550 and there was a dealer-option to supply the serious 6550 tubes.)

6550 is, in many ways, an extra-big 5881 (used in some geetar amps) which is a really-sturdy 6L6 (original recipe) and much beefier than the 6L6GC.

6550 is NOT a drop-in for 8417. It MUST be re-biased. How hot do the 6550s run? What is the voltage on their cathodes? Off hand I think the "200" resistor in the cathodes should be doubled in value and power: 470 10W.

This "stereo" gimmick must have gone with a special instrument. While it has "normal" inputs they appear to be afterthoughts or even deliberately hobbled to favor the "stereo" input. Untangling this mess won't be easy. Especially with the crafty P2P wiring.

[StevieRayVehkakoski]

The 8417:s are no-no because of the price and the lack of availability. The amp now has 6550's but they are physically so big that the right tube is touching (well almost) the output transformer so that's why I'm looking for something else.

I opened the amp last night and checked what's done to the pre-amp and it's quite a mess. The 500k pots on the input tube grids are not there and the instrument- and guitar-channels are mixed together earlier than in the schem etc. so I guess I've got some work to do before really making any plans.

I didn't yet open the power-amp part so I don't know yet what are the actual voltages, cathode resistors etc. All I know that's it's got two big cap-cans that say 16-20-25 and 450V 

[PRR]

> 6550's but they are physically so big

This is a high-power near-Class-A amp. It needs big tubes. Plate dissipation is near 26 Watts per plate.

> tube is touching (well almost) the output transformer

Not a serious problem. The same watts-dissipation in a smaller bottle will heat the transformer just as much, but the glass will run hotter and seal life will be shorter.

Tube Diameters:
6L6GC: 1-9/16
EL34: 32mm (1-1/4")
8417: 1-9/16
6550: 2-1/16 or 1-13/16 (cokebottle or tubular)

Since coke-bottle 6550 are now rare, the difference is 4/16" or 1/4" on the diameter, 1/8" (~~3mm) glass to OT. Probably not enough difference to matter. And perhaps you could oval-out the OT mounting holes and shift it over a few mm.

Yes, it is overall built too tight. However it is still alive 40(?) years later.

What are your plans? Restore to original? Gut it to raw metal and build something normal/common?

[StevieRayVehkakoski]

What are your plans? Restore to original? Gut it to raw metal and build something normal/common?

I'm trying to come up with a plan  The power-amp is fine as it is, I'll check the components, voltages etc. and leave it as it is. Also the reverb part is fine as it is, but then I've got 3 inputs, 2 volume-pots, one master-volume pot and one tone-stack and 6 triodes to play with.. The whole amp is actually in pretty good condition, all original speakers are fine, transformers etc. are original and also the preamp hasn't been messesd with except for the stereo-input so I won't gut it but somethings got to be done the preamp, I can't let 2 tubes just sit there without no use..

I guess I'm worried about the 6550 getting damaged because when it vibrates or when you move the amp it actually touches the OT so it's not leaning to the OT but touching it at times and that might break the glass.

[HotBluePlates]

I guess I'm worried about the 6550 getting damaged because when it vibrates or when you move the amp it actually touches the OT so it's not leaning to the OT but touching it at times and that might break the glass.

Does that mean that the socket contacts are a bit too loose? Maybe the solution is retensioning or replacing the sockets.

[StevieRayVehkakoski]

I guess the problem is that when the tube is pushed all the way in and it's standing exactly straight, it's so close to the OT that you can barely push a paper between them two. The sockets are a bit loose and there's nothing holding it down on it's place so it moves around.

[PRR]

> I can't let 2 tubes just sit there without no use..

IMHO, this cluttered contraption has too darn many tubes.

The attached hack-up will give a happy amplifier. One input with trem, reverb, bass treb volume, and the missing gain. Without the wacky no-bias cathode follower, the afterthought inputs, the silly split-input....

[StevieRayVehkakoski]

I honestly tried to solve the preamp by tracing the wires today for at least 2 hours but I'm not even half way through.. What I can say for sure is that the the tremolo doesn't have the 2N2497 fet it's supposed to have but it has another tube connected to the oscillator. I still didn't find what cathode it actually wiggles so that's going to take some time more.

I'll do it like PRR says except that I'll build the inputs around the instrument and the guitar inputs, same arrangement as in the bassman etc. mixed before the tone-stack and I guess I'll put the tremolo to wiggle the last gain-stage before the master-volume pot. That leaves 3 triodes of but first I need to understand how the tremolo is done because it works right now, it's a bit weak but it works.