Sano Supersonic High Fidelity Amplifier......

[Jack_Hester]

Just thinking out loud.  And, aside from the Tremolo issues. 

I'm going to dig into my stuff and see if I can't make an adapter to test the three inputs on the XLR socket.  Two of them go to V1a, and I have no idea if those triodes are amplifying.  I can pursue that while troubleshooting the Tremolo.  V1 may be the whole issue.  But, I'll treat it as a separate untested circuit, and if it does prove to be the source of the remaining issues, I'll be resolving two of them. 

Plus, I'll have a means to test the other two Supersonic amps waiting on the sidelines.  One works.  The other doesn't.  But, I have no means to test the XLR inputs on them.  More on this later. 

Back to the Tremolo issue(s). 

Jack

[Jack_Hester]

I removed the Pre-amp chassis and have gone back over tube V1, looking for anything missing.  Sure enough, I found a 12K resistor on V1-pin 3.  It fretted me that I did not have a resistor on my drawing, on either cathode of this tube.  Well, there was one.  I have corrected the drawing to reflect this find, but left the revision the same.  I also made a quick check back over the oscillator circuit, and all seems to be in order, there. 

So, I'm back to studying the V1 and related circuitry.  And, beginning to give more credence to what Jazbo8 said in Reply #42:

On some of the Sano hi-fi amps, the tremolo only works on the stereo (aka accordion) input

It's looking more and more like I'm going to have to wiggle the signal V1a-pin 2, to get a response with Tremolo added.  I may have had it all along.  We'll see.  Way too rainy and messy for me to dig around and see if I have parts to make an adapter.  I believe that I have the correct 4-pin plug (female) for this.  A couple of my Ampeg speaker cabs use it, and I had to buy a new one for a cord.  Bought a couple extra. 

Anyway, the corrected drawing is here.  Just like the last one, except for the addition of the missing resistor.  More to come.  Thanks for all the effort, 'til now.  Sure makes troubleshooting easier when more heads are at it.  Have a good one. 

Jack

Update: 10Oct15 - See Reply #54 for the latest drawing.

[jazbo8]

It seems like you are on the right track, one way mentioned to get the tremolo going in these amps is to jumper the guitar and accordion inputs together - not exactly sure how, perhaps they meant with a Y-cable or a jumper cable. Anyway, you should take a look at the Sano 30WR_50WR schematic, but ignore the reverb section and focus on the input and the tremolo sections - I think they looks similar to your drawing even though some of the component values are different.

[Jack_Hester]

I picked up a cable on Amazon, that has a 4-pin female end.  I'll clip part of the cable with that end, and insert it into a small aluminum project box.  I have some small compression fittings that I can use to hold it in the box.  I'll split out all three with phone jacks, and identify.  I'm hoping the small oscillation at V1b-pin 7 is enough for the Tremolo, assuming that I'm successful in finding three working channels.  If not, that will be the next task, to increase that oscillation. 

But, I'm getting ahead of myself.  I'll visit that one when I've proven the channels.  More to come.  Have a good one. 

Jack

[Jack_Hester]

I'm cleaning up an aluminum box that I plan to re-purpose as a j-box for instrument inputs, with a cable to connect to the 4-pin XLR connector on the amp.  I was looking at the circuit again, and I realized that I had not identified the pins on the connector, in the drawing.  That's corrected.  The cable has a female XLR connector installed, but before I start drilling for input jacks and pots, I need to be sure of all the connection points.

Can someone give me their opinion of one of the XLR inputs.  If you you are looking at a previous drawing, the signal ground is pin 4, and the one next to it (pin 3) is the one that I question.  I've included the corrected drawing with pin numbers. 

I question the purpose of this point.  Is it another input?  Or, does it have another purpose?  Before I add a third input, I want to be sure it is one.  Please comment.  Have a good one. 

Jack

Update: 23Novt15 - See Reply #64 for the latest drawing.

[jazbo8]

Pin 3 on Cannon/XLR connector in the 30WRT_50WRT is connected to a small FET, which appears to be missing from your schematic. In any case, it works in conjunction with the footswitch to mute the tremolo signal by shunting it to ground.

[birt]

this is not a really helpful post but just to answer a question you had; the power amp chassis was moved to the other side because it is so heavy and it made the amp more stable when the casters were put on that side.


nice job cleaning up what clearly looks like a well built vintage box of fun :-)

[Jack_Hester]

Pin 3 on Cannon/XLR connector in the 30WRT_50WRT is connected to a small FET, which appears to be missing from your schematic. In any case, it works in conjunction with the footswitch to mute the tremolo signal by shunting it to ground.

I'll drop the Pre-amp out again and look closer.  I haven't seen any SS components so far.  Doesn't mean that I haven't missed some more.  I'll be back. 

Jack

[Jack_Hester]

this is not a really helpful post but just to answer a question you had; the power amp chassis was moved to the other side because it is so heavy and it made the amp more stable when the casters were put on that side.


nice job cleaning up what clearly looks like a well built vintage box of fun :-)

There are a couple rectangular holes in the cabinet.  One on the top, and one on an end.  I used the end hole (close to the newly installed Ampeg handle) for my FX Loop box.  I have a couple badges coming to install on these holes.  I'll post pictures with them, when they're on. 

This has been an enjoyable rebuild, as each fix revealed more of its magic. 

Jack

[Jack_Hester]

Had a chance to fab a box for instrument inputs. 

I installed the first input snd a 500K pot.  Terminal 1 of the pot is connected to signal ground.  Terminal 3 is connected  to the input jack tip.  Terminal 2 is connected to pin 1 of the XLR connector.  I was thinking this to be the Treble channel. 

A second input and another 500K pot.  All is connected the same as the first, except Terminal 2 of the pot is connected to pin 2 of the XLR connector.  I was thinking this to be the Bass channel. 

A third input was connected to pin 3 of the XLR connector, with no pot.  I've pretty much made up my mind that this is not an input.  I wanted to try it anyway. 

I was right about the XLR pins 1 & 2.  Pin 1 is a brighter channel, a bit more than the Instrument/Guitar inputs.  Pin 2 is a very low, dark Bass channel.  Both work very well, but now I'm thinking that I need to address what may be a speaker problem.  There is a strong rattle coming from one of the speakers.  It may be the 15" one, but I haven't gone that far, yet. 

The third input is weak at best.  Weaker than the Pre-amp input.  So, it may be another Pre-amp input.  Or, another switch input for the Tremolo.  I won't chase that one until last. 

I'm pleased with my findings on the XLR channels.  However, I still don't have Tremolo when using either of these.  So now, I'm back to troubleshooting this. 

As stated in Reply #48, I have a very weak oscillation at V3b-pin 7.  Please comment, if you have suggestions on pumping up the oscillator signal.  Thanks. 

Jack

[Jack_Hester]

Been thinking about the plate voltage, on V3a.  125vDC is a bit tame as compared to most of the old Tremolo circuits that I've revived.  Most of those only needed cap replacements.  I'm tempted to strap a 1M resistor across the 330K (~248K paralleled).  Then, I'll take voltage readings and observe the change in oscillation, if any.  Unless someone has thought of another avenue that I should pursue.  Comments, please.  Have a good one. 

Jack

[jazbo8]

Try disconnecting the output of the tremolo after the coupling capacitor, so it is not loaded. Is there a tremolo output when un-loaded? It should be more than 10Vpeak.

[Jack_Hester]

Try disconnecting the output of the tremolo after the coupling capacitor, so it is not loaded. Is there a tremolo output when un-loaded? It should be more than 10Vpeak.

I'll check that out when I'm able to go back in.  Should be sometime this week. 

Jack

[Jack_Hester]

It's been a little over a month since I put my hands on the amp.  Got some time off in the upcoming week (Thanksgiving holidays), so I can spend some time on it. 

This afternoon, after Church, I will pull the pre-amp chassis, and make a closer inspection of all connections to the tubes.  I know that I have oscillation (V3).  But, is it enough at the grid of V1b? 

I'm hoping that there will be an overlooked connection related to the enable/disable of the oscillation at V1.  The other 50WR schematic has a solid state component that I haven't seen on this amp.  But, that's not to say one isn't buried in the very dense p-p wiring.  Most of my hand-tracing has been with a meter, to locate the ends of each connection.  Close visual tracing is some difficult.  But, it's time to resort to that. 

Anyway, I'm still pursuing the fix.  All the rest of the amp functions are very satisfactory. 

Jack

[Jack_Hester]

I've been hand-tracing this afternoon.  No sign of any FET component on the pre-amp chassis.  Did find a foolish mistake.  I had R10 (over in the Tremolo) drawn incorrectly.  However, when I went back and looked at my very first literal drawing of the chassis layout, I have it drawn correctly.  So, at some point in my redrawing it to this format, I inserted it wrong.  Correction is shown in attached drawing.

I'm still looking the layout over, as I have been concentrating more on what was connected to V1.  Now, to spend some time around V3. 

The footswitch is connected like I have it drawn.  No idea as to how it's muting the Tremolo, but I'm satisfied that whatever it's doing, pin 3 on the Stereophonic Input is there for the same reason. 

More when I make new discoveries.  Have a good one. 

Jack

Note: 25Novt15 - If you downloaded 'rev E', trash it.  'rev D' was correct. 
        The one that I attached in Reply #67 has components moved for clarity.  But, still the same as the last 'rev D' posted

[Jack_Hester]

In my 'rev E' drawing, can someone explain why the oscillator takes two paths to the grid of V1b? 

It appears that C3 is normal for a coupling capacitor, to prevent DC from going downstream to the grid.  And, I'm thinking that everything between C3 and the grid is some type of filter. 

However, R10 is a direct path for DC to get to the grid.  This looks wrong.  But, it's there.  Once again, I'll go back and trace this to see if I've overlooked another component. 

But, I would like some comments on the above, and I'll report back with my findings.  Thanks for all help.  Have a good one. 

Jack

[sluckey]

It appears that C3 is normal for a coupling capacitor, to prevent DC from going downstream to the grid.  And, I'm thinking that everything between C3 and the grid is some type of filter.

I agree.

However, C10 is a direct path for DC to get to the grid.  This look wrong.  But, it's there.  Once again, I'll go back and trace this to see if I've overlooked another component.

Say what??? A cap is never a direct path for DC. Furthermore, C10 is the cathode bypass cap for V3a and has nothing to do with getting the signal to V1b.

EDIT... I see you edited your post so I will too. I believe R10 is drawn wrong. What dc voltage do you measure on V1b pins 7 and 8?
 

[Jack_Hester]

Well, Crap!  I should have trusted my last drawing (rev D), as I had R10 in the correct place.  And, the original drawing, that I thought was correct, ain't.  So, for anyone who downloaded rev E, trash it. 

I did go back on rev D and make the V1 and V3 drawings more literal to the actual build.  Meaning, more wires  to V1b grid, rather than showing them tied at junctions and just one wire attached.  This was more for my keeping things straight when I compare the drawing with the actual.  Also, I moved the components C2/R13/R14 over to V1a-pin 3, where they actually attach.  I had them drawn to V1b-pin 8, just because it was easy to draw.  Pin 3 and pin 8 have a jumper between them on the actual tube socket. 

So, R10 does indeed connect to the junction of C3 and R11.  And, the other end of R10 connects to the junction of C1 and R8.  Then, a wire goes from junction R10/C1/R8 to V1b-pin 7. 

A wire connects the wiper of R9 (lug 2) to V1b-pin 7.

And finally, one lead of Choke T2 connects directly to V1b-pin 7.  And, the other lead of T2 connects to R12. 

Now, I'm back to square one.  The voltage readings on V1b-pins 7 & 8 should be the same as in reply #48.  I'll take them again, when I get the chassis back in the cab.  And, I'll take a reading at the junction of C3/R10/R11.  Hopefully, I'll see a decent oscillation there.  More to come. 

Jack

[Jack_Hester]

While I had the chassis out, I removed C7.  At some point, I burned it with the soldering iron.  I don't think that I damaged it, but I could see the metal foil.  So, I will replace it on Friday.  I didn't figure that it would affect my troubleshooting. 

With the chassis back in, and connected, I let the amp warm up.  Voltage readings were taken with my VTVM, so that I could observe oscillation better.  Reading are as follows:

V3a - pin 1:                     oscillation around the 135vDC mark.
Junction of C3/R10/R11: oscillation 0.6 to 1.4vDC
V1b - pin 7:                    oscillation 0 to .18vDC
V1b - pin 8:                    steady 7.8vDC

Still no Tremolo.

Before I decided to put it away for the night, I grabbed a 12AX7 that I could see no brand visible.  Swapped it out with V1.  Warmed the amp again, and connected the guitar. 

I have the most amazing Tremolo! 

Probably not any more amazing than that of other amps that I have.  But amazing, because I'm hearing a strong Tremolo for the first time.  I'm too brain-tired to enjoy it right now.  And, I won't be turning it on tomorrow.  But, I will replace C7 on Friday and give it another workout.  I may have had it the last time I was in the amp, but I didn't think about trying another tube in V1.  It was new.  What could be wrong? 

The Tremolo footswitch works fine.  Wish that I could figure out how it mutes.  Reverb is very strong, and that footswitch works fine.  The drawings don't reflect it, but this footswitch grounds the signal at the wiper of the Reverb Volume pot. 

I'll put it away for this evening.  Time to give it a rest.  This has been more of a workout trying to make correct drawings, than troubleshooting.  And, I'm curious about the JJ tube.  Did I damage it, at some point?  Or, did it just give up?  I'll put it on the tube tester and see what it shows.  Anyway, I'm gone.  I'll be back on Friday with more.  Have a good one. 

Jack

[Willabe]

Alright! Wuba, wuba, wuba.   

[Jack_Hester]

Y'all didn't think this was over? 

I soldered a new .047uf cap in for C7, so the amp is once again whole.  Verified the Tremolo as working.  So, it could be considered finished, as far as functionality.  I cleaned the back panel and spray painted the four large round holes that were drilled in the upper part.  Vent holes, I suppose.  I had the wife go by Lowes Home Improvement, and pick up some charcoal grey aluminum screen wire.  A burger came with it, somewhere along the way.  Stapled the wire to the inside, so now it has a closed lookl  But still functional as vents, if that indeed was the purpose. 

This amp is some loud, though most of my testing and playing has been at half of the Master Volume.  But, it is clean all the way up, no matter the setting of any volume.  It is working fine, but I still wanted to swap the unknown brand of V1 that I inserted, with another JJ.  Guitar Center was closed in Greensboro, Thursday afternoon.  We were over there for Thanksgiving.  Didn't go anywhere yesterday or today.  So, digging around, I found any number of old stock 12AX7's, and two new Sovtek.  Out came the brand X V1, as well as the 12AU7 in V2.  Installed the two new Sovteks, as I wanted to see how the amp sounded with a bit more power in V2. 

Woke it right up.  Even at half Master Volume, it's now noticeably louder.  At full Master Volume and any of the other levels at full, it's still plenty clean.  I didn't play very hard, so I don't know if it will break at the high levels.  The two new tubes will stay in, but I need to stock up on some more new 12AX7's. 

I left V4 as a 12AU7, as the Bass is ever so deep on that channel.  I can't see a need for any more power there. 

Anyway, it goes to Church in the morning, for show and tell.  Mostly for show, but I'm hoping someone will give it a try with an electric.  Our music leader, Don, only uses acoustic for Sunday service.  More tomorrow afternoon.  Have a good one. 

Jack

[Willabe]

Anyway, it goes to Church in the morning, for show and tell.  Mostly for show, but I'm hoping someone will give it a try with an electric.

I want to go to your church!   

[John]

A burger came with it, somewhere along the way.

You have a good wife!

[jazbo8]

Great to hear that you got everything sorted out, it's a keeper!

[Jack_Hester]

Great to hear that you got everything sorted out, it's a keeper!

Yesterday, during the break before Service, Don connected his hand-built Tele and gave it a shakedown.  He liked the Guitar/Instrument channels, but mostly the Treble channel through my adapter for the XLR connector.  It is a bit brighter, and the Tremolo works only through this input.  He really liked the Reverb.  Overall, he said the amp sounded really good. 

Another member, Steve, has a Bass guitar there.  He doesn't play, but has it on loan to the Church.  We connected through the Bass channel on my adapter.   Don was impressed with that, as he said it had an 'old time' bass sound.  I don't know what that means, but I'm glad it does.  I pointed out that the 15" speaker had a rattle to it, when I had the volume turned up.  Don proved otherwise.  With the Master at only half volume, he made it rattle when he played it rather hard.  Got another 8 ohm Utah on the way.  Hope it is the fix.  This speaker has no visible defects.  What would make for this rattle? 

Anyway, Don stated the same as you.  "It's a keeper!" was his opinion.  So now, it's in the bedroom for my playing pleasure.  I can close off the world and not worry the wife.  Think I'll practice some Christmas songs.  Start the Season off right. 

Jack

[Jack_Hester]

Early in the week, a replacement for my 15" speaker came.  Another Utah, but this one has what appears to be another speaker in the middle.  A tweeter that is coupled to the main by means of a capacitor.  I'm guessing this one to be from the 70's, as the badge says '50 Years of Service'.  The one that I removed says '40 Years of Service', and I'm satisfied that it was original to the amp.  I can find no good history on Utah speakers, to confirm when the company started.  The speaker code is 328603, making me think that this one was made the 6th week of '73.

Anyway, it's installed and sounds good.  I really can't tell much difference from the other one.  Makes me now think that the smaller (8") in parallel with this one is the source of the rattle, when using the Bass channel.  Oh well.  Maybe the amp wasn't intended for serious Bass usage.  Pretty sure it began life as an accordion amp.  I won't do it today, but I'll put the original back in and save this one for another project. 

With the exception of swapping back to the other speaker, I'm thinking all tweaks are done on this amp. 

Summarizing, what a trying, but very wonderful restoration.  Back to something approaching an original build.   Really good guitar amp, especially through the Treble input.  Reverb works for all channels, as it is driven from the speaker output of the Power amp.  It's output into a separate 8" speaker.  Tremolo works on the Treble channel, only.  Bass channel is dark and deep, and would probably work very well mic'd.  I still don't know how the Tremolo is muted, but it works.  From the dedicated footswitch jack on the faceplace, and from pin 3 on the XLR jack. 

Quite possibly, if you find an Excelsior of the same model (30WR-50WR), my schematic may match that build. 

I have another one of these Sano Supersonics, a bit newer.  Faceplate looks some different, though it has the same model name.  I'm thinking latter 60's, but will confirm that when I go inside that one.  I'll start a new topic when that takes place.  Don't be looking for that one, just yet.  Stuff in front of it. 

Jack