Now have Hughes and Kettner Switchblade 100 schematic

[bnwitt]

Does anyone know where to get a schematic for the H&K Switchblade 100 amp?  I've got one in the shop that powers up, has all switching and indicators working but no output.  Speakers, OT and power tubes are good, preamp tubes are good.  It would be nice to have a schematic before I hook up the generator and tracer.  Man even getting the chassis out of this amp was a major hassle.  PCBs and ribbon cables too.  I hate working on amps like this.

Thanks,
Barry

[Dave]

I have no idea where to get a schematic for that thing, but I might have some insight.
I don't know how you are concluding that the OT is good, but I have come accross two OT's in my day that tested perfect in every conceivable test except the one where you hook it to a speaker and wait for sound to come out.

Dave

[bnwitt]

Well how long is your "day"?   Are we talking 5 years or 50?  I've been doing this electronics thing for around 40 years and the tube amp stuff since 1994 and I've never seen that but I don't doubt your word as I've seen some pretty strange stuff myself.  I checked the OT with an ohm meter and the resistances look good.  I hope you're not right on this one.  

Any way, I did a little signal injecting and tracing today.  The main input and processing board is doing everything it should and is sending signal on to the effects send and return board along with the power/preamp board and I've got strong signal on the V1a grid but zippo on the plate.  I got side tracked before I could check voltages on that stage but I'll do that in the morning.  Boy a schematic would really help on this thang.

[John]

http://safemanuals.com/user-guide-instructions-owner-manual/HUGHES%20%2526%20KETTNER/SWITCHBLADE%20HEAD%20100%20COMBO%20100%20COMBO%2050-_M

So far, this is the only thing I've been able to find that looks like it *might* steer you right. I'm on dialup here at home so that fancy java-whatever in the lower right corner won't load for me. Might be nothing more than a manual. Hope it helps!

[Dave]

The first time I saw it, a guy brought me a Soldano Avenger that he wanted a second opinion on. He had an estimate from a well known tech saying that the OT had burned primaries.
I took the OT off and tested with a meter and it looked ok. Then I used a variac to check turns ratio / primary impedance, and again everything looked fine.
I put it back in and labeled the "well known tech" as a quack and spent way too long trying to trouble shoot the amp to no avail.
Oh, but wait, on second thought, let me try a generic 100 watt OT and see what happens. Voila! worked like a champ.
So, I internally apologized to the "well known tech" that I had internally judged.

Another time, I had the same problem on a Twin Reverb.

Dave

[bnwitt]

Well it just goes to show you the only way to test anything is under actual operating conditions.  Well anyway, I emailed H&K yesterday and this morning in my email I had a 45 page service document for the Switchblade 100 combo so I'm good to go.  Thanks everyone.

[bnwitt]

Well I guess I was over thinking this amp problem.  I checked the power tubes in my tester and one of the 4 was pulling right at max amps at 400vdc plate.  The set was 51,45,45,44 respectively.  Checked the HT 630ma fuse and it was blown.  No other apparent collateral damage in the amp so after I receive my order of GDC T630ma fuses (what and odd ball fuse)  this baby should be ok.  But at least I now have a service manual on the amp if something else brings it back to my shop.