help with the SM-1 module please

[SaeWolf]

the module highlighted in the picture (in a hurry just highlighted it in paint) is somehow screwing up a 1965 sunn sceptre,if anyone can examine the picture and please help it would be much appreciated...also the pencil date of the head is march 17th 1965,the year the company was founded,so if anyone who's familiar with that year model knows of any spec. differences between the 1968 spec and the 1965 model please help out...

[EdBass]

I'm pretty sure that there was no 1965 Sceptre. I think the first year was 1968, post a pic of your amp and that will tell the story.

In what way is that module "screwing up" the amp? That's the optocoupler, it's for the tremolo circuit and it should only really effect the tremolo's performance.
The bad news is that those units were actually fabricated by Sunn out of two components, so rather than being an outsourced component that you may be able to find available, they were a "custom" component.
There are options, but first you should probably post a pic of your amp to make sure everyone is on the same page here.

[SaeWolf]

ok,heres some pictures,to let it be known this isnt my amp i know i said it was but its actually my dads amp,you see his electrically intelligent,computer illiterate,im the opposite,so together im trying to help him resolve his issues,sorry for not stating that soon,also sorry it took forever to repost to you,i work alot,but i got pics,hopefully they'll upload,now for the diagnostic run down from my dad...
amp was functioning fine up until a kid plugged into it with a massive amount of Cinderella boxes(a coffin of effects pedals) and max all the settings on the head while rehearsing, replaced a vast majority of faulty parts but now no so sound at all is coming out,the assumption is its coming from the pre-amp stage,so far every time its kicked on it burns out the 6.8 killaohm  and one time it burned the 10k. as well... as for the stuff working is the power transformers giving voltage,outputs giving voltage,the power tubes fire up,no problems coming from rectifier tube,   any ideas and thoughts???

[SaeWolf]

more pictures,sorry for the bad spelling,im typing in the dark most of the time due to my color setups on my comp...

[EdBass]

First off from the pictures I'd say that's a 1969 or newer Sceptre, I can see the mid-boost switch. Secondly, in all honesty I'm really having trouble deciphering what you are typing about. Without punctuation and capitalization it’s extremely difficult to read, and even once I do suffer through it, I really don’t know what you are talking about anyway.
Where are these “6.8 killaohm” and “10k” (I assume resistors) you referring to, and what is a “Cinderella box”. There are a whole bunch of resistors in that amp, and using (local?) slang isn't helping anything either.

Here’s what I suggest: Search "optocoupler" using the search function on this site, and then take the amp to a local qualified tech and get it fixed.
I’m sorry, but I don’t really see this getting resolved on this, or for that matter, any online forum. I know that I personally can’t follow what you are saying.
There are some very knowledgeable, experienced tech members here that may be able to follow your style of communication towards remedying your Sceptre issues... But I’m not one of them.

Good Luck!

[SaeWolf]

okay,I edited the schematic for you to show the locations of the resistors for you. I'm sorry if my grammar or punctuation are off,I'm doing the best I can. As for Cinderella boxes I put in parenthesis that it's referring to a coffin of effects pedals for guitar. Literally think of a coffin that a DJ mixing bored is in,the kid had that many pedals,my dad wasn't there to stop the kid. My dad left the amp on accident at a friends studio after rehearsing, by the time he got there the next day to pick it up the kid had already damaged the head. I hope this helps clarify a little,and i am sorry that about so many typo's in my previous posts. But like i said, the assumption is that the problem is coming from the pre-amp, everything is checking out fine,but those resistors keep blowing out every time he turns the amp on. I know it's a shot in the dark but can you help?

And I intend on looking up the octocoupler, thanks for that one, is there anything else off the top of your head or anything that stands out in the photos? If not it's okay, I appreciate you're help thus far.

 

[EdBass]

Look, you really can't diagnose a busted amp on an internet forum. But since you are so persistant, let's make a game of it; I'll take a shot...

Something is drawing too much current through that filter circuit if I understand you correctly that all of those big resistors fry when you fire the amp up. It could be a few things, but if I had to make a one component guess, it would be that the 20uf 450V cap being fed by the 10K 1W resistor, or one of its leads is shorted.

Who's next? One guess per poster! 

[loudthud]

Read this thread: http://sunnforum.ampage.org/sdp/index.php/topic,4836.0.html

The part you are holding looks like the later part. That part was actually a solid state relay. You can still find them on the internet but they are expensive.

This thread: http://sunnforum.ampage.org/sdp/index.php/topic,4772.0.html has more troubleshooting tips for dealing with a bad tremolo. When the light bulb inside the tremolo bug fails, the amp goes almost silent because it is in series with the guitar signal.

[EdBass]

Read this thread: http://sunnforum.ampage.org/sdp/index.php/topic,4836.0.html

The part you are holding looks like the later part. That part was actually a solid state relay. You can still find them on the internet but they are expensive.

This thread: http://sunnforum.ampage.org/sdp/index.php/topic,4772.0.html has more troubleshooting tips for dealing with a bad tremolo. When the light bulb inside the tremolo bug fails, the amp goes almost silent because it is in series with the guitar signal.

Great info on the tremolo; but what do you think is causing the resistors across the filter caps to fail at startup as indicated in the second schematic?
Based on what I can decipher from the OP’s posts, I would think that would be the primary issue to address.

Edited to fix links in quote LT

[loudthud]

I would have to agree with the bad filter cap as the first place to look. There could be a short in the B+ somewhere or something like someone installed the wrong tube or something wacky like that. Pretty straight forward to track down with an ohm meter.

[Isaac]

I find myself wondering why he is so sure that there is a problem with the optocoupler.