Sunn scepter head 1969 trem problem

[Soundmasterg]

A Sunn is a good amp for use with pedals....other good ones are HiWatts and Vox AC100's and AC50's. I made myself a clone of an AC100 that is fantabulous, though it isn't done yet. Anyway, once you get it dialed in, I bet the Sunn will work fine. If the roach is bad, you can make another, but you need to know some specs of what is there so you can get the correct parts. I can see if Conrad has any ideas for you on this problem if I talk to him soon. If I get a chance to talk to him and he has anything to add, then I'll just tell him to post here BD.

Greg

[Baddog]

I made a matchless spitfire out of organ amplifier that sounded prety nice. I gave it to a friend of mine who was in a rut with his guitar playing . I had my brother make a head cabinet for it . Looked like a small marshall head but with less knobs. I have 8 or so organ amps sitting in my basement .  Hmm
Do I see another spitfire in my future... Not a pedal amp but a nice well rounded amp with the master volume. You could pull off some nice country licks or get down and dirty . Oops rambling on again.
I went to ratshack and picked up some 1000uf caps for the filter section and a couple 10uf's . that's about all they had I could use. I have some 50v panasonic caps I might try for the 1 and 2nd caps . How do I know If the trem bud is bad?
Thanks again greg

[Soundmasterg]

I made a matchless spitfire out of organ amplifier that sounded prety nice. I gave it to a friend of mine who was in a rut with his guitar playing . I had my brother make a head cabinet for it . Looked like a small marshall head but with less knobs. I have 8 or so organ amps sitting in my basement .  Hmm
Do I see another spitfire in my future... Not a pedal amp but a nice well rounded amp with the master volume. You could pull off some nice country licks or get down and dirty . Oops rambling on again.
I went to ratshack and picked up some 1000uf caps for the filter section and a couple 10uf's . that's about all they had I could use. I have some 50v panasonic caps I might try for the 1 and 2nd caps . How do I know If the trem bud is bad?
Thanks again greg

I've got a bunch of organ amps and projects sitting around too. Not enough time to work on them with going to school for engineering, but have been working on a Bogen CHB100 that I gutted and modded for something I can use live at the jams. Its pretty cool and unique with a light up nameplate, a parallel input stage, 5879 pentode, and a quad of 7868's....58 watts RMS. It will be getting power scaling needless to say...haha.

I'm not sure how to check if the trem bud is bad honestly. Might do a search on the other areas on Ampage or on other sites like AX84, or Hoffman, or do a post and see if you get any help.

Greg

[Baddog]

I've had some pretty good scores as far as organs and stuff like that goes. I hooked up with a guy who owned some storage units. One of his tennents who was renting 6 storage units had died and his family didn't want anything to do with the stuff he had in storage. The units where full of organs , old stereos , clothing and prety much anything gun an imagine. The guy was a pack rat to say the least. I helped the guy clean some of the units and he gave me what I wanted out of them . I hit about a 5 gallon bucket full of tubes and one organ had around 20 telefunken 12ax7's inside . J was like a kid in a candy store . Anyone else would have seen junk but I saw treasure but know with shows like Storage Wars and Pawn Stars all those days are in the crapper. ..

http://a4.l3-images.myspacecdn.com/images02/20/a61f7329d7984d4daf63a45e4a32b7b0/l.jpg

http://a2.l3-images.myspacecdn.com/images02/93/d03630d4d51042d7a95b95ec98bfd9bd/l.jpg

[nshallcross]

Hi, new member here and just thought I join the forum to chime in on this topic.

I too had a sceptre with a similar problem- clicking in the tremolo that would cut in and out with variable intesity depending on the rate and depth settings. I bought this amp after it had just been done over and some of the major stages had been recapped but not the tremolo circuit.

I found this post describing some similar problems- http://sunn.ampage.org/sdp/index.php/topic,2071
and so I decided on trying to fix it by replacing the 2 1000uf 35V electrolytics on the trem board.

Just finished up about 10 minutes ago and so far so good! I haven't really put it through it's paces yet, but it holds up ok with a p-bass through a little 2x12 with the volume at about 4/5. I usually run my sunn's (I also have a sonaro) pretty close to wide open when using them for bass, and right around 7/8 for guitar. I'll report back after a full run, but replacing these caps seems like a good fix for this kind of problem. Probably a good idea even if you haven't run into trouble with them yet...

[Baddog]

Hi, new member here and just thought I join the forum to chime in on this topic.

I too had a sceptre with a similar problem- clicking in the tremolo that would cut in and out with variable intesity depending on the rate and depth settings. I bought this amp after it had just been done over and some of the major stages had been recapped but not the tremolo circuit.

I found this post describing some similar problems- http://sunn.ampage.org/sdp/index.php/topic,2071
and so I decided on trying to fix it by replacing the 2 1000uf 35V electrolytics on the trem board.

Just finished up about 10 minutes ago and so far so good! I haven't really put it through it's paces yet, but it holds up ok with a p-bass through a little 2x12 with the volume at about 4/5. I usually run my sunn's (I also have a sonaro) pretty close to wide open when using them for bass, and right around 7/8 for guitar. I'll report back after a full run, but replacing these caps seems like a good fix for this kind of problem. Probably a good idea even if you haven't run into trouble with them yet...

Every electrolytic cap has been changed in my amp... I have a pulsing sound not a ticking sound.... The pulsing sound is there with the volume and trem on zero. I also get a little guitar signal with the volume at zero . I think i might have a bad trem module and might just disconnect or bypass the dam thing and say the hell with it.  If i turn the trem up the pulse does speed up but I'm thinking I shouldnt hear anything unless a signal is applied. Im also doing my testing without the reverb tank hooked up but that shouldnt make a difference....

Thanks
BD

[Soundmasterg]

Is there a footswitch to disconnect the trem circuit or not on this thing, or any jacks for it on the amp? If you don't see one, then you can just pull the oscillator tube and the noise should go away. If it doesn't then the problem is somewhere else. See if pulling the phase inverter tube makes it go away...if it does then you know for sure it is before it....see if you can use this approach or shorting out one grid at a time to see if you can localize where the problem is. It will make it much easier to solve BD.

Pretty cool pics on the organ amps...looked like you might have had a Conn in there? (2nd one in front on the right) If so they usually had really nice transformers...Foster often, Schumacher sometimes. Fosters are really good btw....made in Cinncinatti and the company is still around and in business, though I don't know if they are doing tube amp stuff anymore or not.

Greg

[Baddog]

I'm sure there was a conn or two in there some where . I usually get Hammond with a Baldwin every once and awhile . I also get some nice speakers as well like 15" , 12" and 10" jensens. I think those days are gone though.

I groundedout the footswitch and the problem was still There. I hate typing from my phone. I do some other checking tomorrow  or I should say later today.

Thanks
Bd

[Baddog]

I tried shorting out the footswitch jack and the problem is still there. I pulled the phase inverter and the problem is gone. I pulled the 12au7 reverb driver tube? And problem is still there . I pulled the preamp tube and problem is still there. I pulled one tube at a time and put it back in and pulled the next.
I didn't mention it but i just had a baby girl October 14 of last year so that's why it's taking a while to fix this amp. I can only go in the basement and work on it in spurts. I'll try the shorting method tonight or tomorrow .
Thanks again

[Soundmasterg]

I tried shorting out the footswitch jack and the problem is still there. I pulled the phase inverter and the problem is gone. I pulled the 12au7 reverb driver tube? And problem is still there . I pulled the preamp tube and problem is still there. I pulled one tube at a time and put it back in and pulled the next.
I didn't mention it but i just had a baby girl October 14 of last year so that's why it's taking a while to fix this amp. I can only go in the basement and work on it in spurts. I'll try the shorting method tonight or tomorrow .
Thanks again

Congrats on the baby girl BD! I understand completely.

So its before the phase inverter, but after the preamp tube then where the problem is, which could be the roach for the trem since it works after the first gain stage. I'm not sure how to check those roaches and don't know if the fender bug works or if you need another. I may have to talk to Conrad in the next couple days so I can ask him if he remembers....

Greg

Nevermind about asking Conrad...he posted in this post about how they made the roach.... http://sunn.ampage.org/sdp/index.php/topic,2071.0.html

[Baddog]

I might just bypass it by the volume pot and see what happens . If the problem disappears than I should be the trem module.

[Baddog]

I jumped the footswitch again and it did quiet the pulse but not eliminate it. Maybe the trem is getting amplified to ground and somehow getting Bach in the signal chain somehow.




Well I tried bypassing the trem at the volume pot and it didn't work ( still had the pulse ) so I disconnected the power from the board and pulled the 12au7 for the reverb. I'm thinking about ordering some transistors for the board.

The amp has some serious ground issues for sure. If i drag my fingernail across the chassis i can hear it in through the speakers. 

[Baddog]

I took voltage readings with the 12au7 removed and the B+ jumped way up. Hmmmm I put the tube back in and the B+ went back down. Is this normal?
How much of a voltage drop should I get across the choke? It's a 60ohm choke.

[Baddog]

Still messin with the Sceptre. The voltages in the amp are to high even for the second filter stage ( 500v Cap ) to handle so I built a voltage browner with parts from Ratshack. IT drops the 120v ac to 112v ac . Here are my voltage readings with browner
112v ac
Bias 45ma @ 500v plate
6v ac heaters
  
Filter Stages
505v  1st
497v   2nd
398v  3rd
315v    4th
279v   5th
If my brother really likes the amp I might have him buy a V-Dump from Weber Speakers.
Trem is still pissing me of to no end.  All I know is the trem board adds allot of noise to the amp. I mean allot of noise.
I did have the voltage increase problem again when I was in the basement messing with the amp. I have all of the tubes in and it jumped up like 100v across the whole amp. I'm talking 400v on the 5th filter stage. But I shut the amp off and try it again and the voltages are back to normal. This only happened one when I was down stairs today. I wonder if running the 2nd filter stage over 500v for a wile damaged the 2nd stage filter cap??  
I also had a weird thing happen. I got a noise through the speaker that sounded like Morris Code. Hmmmm  I had this happen once before when I was working on the am[p. I did have my cell phone close to the amp when I was working on it.

Thoughts welcome
BD