Would this be right for the old V1?
Or am I out to lunch?
Don't know how to do pin6.

 
     

Is V2A the old V2B?

It's very cool stuff!
I really appreciate your help
A bit over my head but I am learning a lot.
At this point I don't know what to do with this amp if worse comes to worse.
Is it a piece of junk design wise?
I was thinking of putting in a ceriatone board, but I don't think it will fit.
The chassis on their design is too big.
What about making a new pcb? Perhaps based on your design?Dumb idea?

It could be like you said before that it needs some kind of dc voltage or reference on the filaments to kill the hum. That would seem to be the only solution.
My tech will tell me next week what the story is on this amp.
I'm sure he can fix this thing.

If he fixes it, do you see ways of improving it by changing values?
That's something I could do.
If you could finish off the schematic you'd be doing me a huge favour! 0:)
I simply don't have a clue how to do it.

The funny thing is that with the reissue mullard power tubes it actually was very touch responsive. One thing I did before was put in a High gain ruby tube after the phase splitter, which seemed to reduce the gain down a little and smooth it out.
What about a 12ay7 in v1?
Yes the transformers are tight. But I wonder why the fellow who has the same amp doesn't have these problems? That's what I don't get.

This is getting interesting!
I'm kind of chicken to cut traces though.
Next week I'll find out what's up on this amp.


What I seem to be getting is that the lack of schematic is
making it a bit tougher than usual to follow the signal with the scope.
It's coming from the power supply though.

It's interesting that you're cutting the same two traces as before,
but I can tell you the hum was still there almost as bad.
There was also very little gain.Low gain in my opinion for lead.

There was no buzz with the distortion however.
There were two low pass filters on the preamp on the input and output, were they there
to eliminate the buzz? There is high static on this amp.
If so they worked.

Could it be that on rednefceleb's amp the board is slightly different?
Would too high voltage on tube 4 cause buzz?
How  tough would it be to get rid of all those connectors?

The center tap is grounded and the voltages check out from the tubes.

From what I was told the diodes, tubes caps are all good.
He suspected the transformer because this was the case with a Marshall amp. They installed the wrong part in that case.

But two techs agree it's coming from the power supply.
But what exactly do they mean?I believe he checked all the pins and so on and it was good.
One said that there was a glitch on the board the diodes tested good but they shouldn't be.
Could the transformer be faulty somehow? I think he's going to test that next.

Okay. I think it's the wrong output transformer.
According to information I have from someone who has a hum free Hiwatt it's supposed to be an output transformer labelled MOT 21 GT C310.
Mine is labelled MOT 21 GT 0310 . Don't know what the difference is.
Would this cause these problems I've mentioned?
The Power transformer labels match.
Any ideas?

Amp is with my tech right now.
There's absolutely nothing wrong with any parts on the board or the tubes.
Tube 4 has 350volts instead of 285 however. Can this cause buzz?
The hum seems to be coming from the power supply. Any ideas?
We thought it might be a too small output transformer or they installed the wrong one but the numbers match the tranny's on someone else's Hiwatt amp and he has no hum.

Would it be possible to upgrade the reverb tank?
It's about 9.75 inches long and has two springs.
The only markings are:
In 600
Out 2.2k
SH-250

Does accutronics make something?
Also thinking of using silver mica caps instead of the ceramic ones in there.

would changing the ceramic disc caps in this amp to a better quality like mallory have an effect?
There are 7 in all: 47pf, 3 x 470pf, 2 x 1000pf, and 220pf. What voltage should they be?
These just have the number and that's it.

where can I get that? It's a cliff jack that's in there on the board.
Would the jumper connecting the two jacks also be a factor?

How would I install that?
As for the distributor, all I get is we don't distribute Hiwatt anymore so take a hike.
Would upgrading some components improve the amp?

Well I have problems not only with the tube Hiwatt but this solidstate one.
This was "repaired" under warranty 4 times. Warranty is kaput right now.
Right now I occasionally get the radio on the high input jack.
If I push in the guitar cord in and out a few times it will go away for quite a while.
Still, what's causing it?
Is it a loose jack?
They jumpered the ground between the high and low jacks.
Also they added a jumper on another spot on the board looks like for another ground issue.
Also, the mid control with the distortion on, works backwards,10 to 0, but  with distortion off, works normally 0 to 10. Of course Hiwatt has not sent me a schematic. They should have one but...

Thanks for the info it is much appreciated

I tried to put in a speaker that was as close to the Fane spirit as I could find.
I also put in an original Mullard phase splitter 12At7.
I put in an eminence ramrod 10 inch which actually I think is more like a celestion 12 inch.
The frequency response is like that of a 12 inch. If you use the Mullard el 84 reissue tubes from New Sensor, you get a tremendous bass sound, very much like a 12 inch speaker.

I looked at the celestion 10 inch speakers but the price was a little steep and the reviews not so incredible. Right now there are jj power tubes in there, but I think the tone is actually better with the Mullards. You lose some rock edge though. Of the new preamp tubes I tried,New Sensor Tung Sol seemed to sound best but didn't last past 4 months without microphonics at high volume. One thing I found was if you put in a high gain tube after the phase splitter like a Ruby tube 12ax7, you actually clean up the distortion and get a smoother singing sound. Right now there are Mesa Boogie chinese 12ax7's and a mesa boogie Sovtek after the phase splitter. The tubes tested bad so they were replaced.

But I think this week we'll know exactly what's going on with this amp and if there's a solution or whether I might have to throw in the towel on it. Maybe the Egnater Rebel 30 is a good alternative or Mesa Boogie 5:25?

Here's a schematic of the sa412.


Could you explain more about the front end?
It's a bit over my head.
I just thought in a general way a bit of something here and there.
Was the person who cut the traces attempting to do what you say?
Is the gain all coming from tube 2 on this amp?
I think that this amp is a reissue of the american sterling import amp.
But how much that resembles a hiwatt I don't know.
I was thinking that if I get bad news about the repair, how tough would it be to maybe stick the trinity amps triwatt in there or the ceriatone board?
Can dc power even be done on this amp and if so what would the cost be?