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Very Old SWR Schematic needed

iriegnome

iriegnome

Bassstar style
Supporting Member
Nov 23, 2001
11,263
5,579
61
Kenosha, WI 53140
#1
I have a 1986 SWR SS-180 that I need a schematic for. SWR has no information on anything newer than 1992.
I have posted this before without any response, so I am really hoping that someone can help.
I need a SWR SS-180 schematic. Can anyone help?
Yes, I all ready did the google seach and on and on. Nothing that I could find.
Any help will be appreciated.
 
#3
Just curious what you need the schematic for? I'd be willing to bet you can find a lot of similar circuits in the Studio 220 or even the SM400 as they'll be easier to find Schematics for. I think the only difference would be in the EQ circuit depending on what your looking to do with them. Steve Rabe used to reuse circuits and simply modify them for different amps back in the day. Just a thought if you don't have any luck getting the original SS-180.
 
#7
If you find that 220, could you send it to me? I have a couple of postings around the net with that SM-400 schematic. I think it is from 3 or 4 years ago. I still get e-mails asking for it. We need a sticky in Amps for us to post schematics. For any and all of us to be able to hopefully find what we need. Personally I like having it to have it just in case. I am kind of crazy like that though
 
#9
Hi.

Found the Studio 220 pre amp schematic and the PS schematic.

The former fits into the attachment limit, the latter doesn't :(.

No power amp schematic yet.

I put the bias procedure .pdf here as well

That's a very good idea about the schematic library on TB. Most of the schematics can be found on the 'net, but all are scattered around and usually the bass amps are the hardest ones to find.
Not too many available for SS amps either.

Regards
Sam
 

Attachments

#10
Thank you. I did not even see this posting until now. I will forward on the prints to the guy working on my 180. Hopefully they can work. I think the issue is with the bias pot's. They are kind of unusual in a single tube preamp config, but hey, it is SWR
 
#11
iriegnome said:
Thank you. I did not even see this posting until now. I will forward on the prints to the guy working on my 180. Hopefully they can work. I think the issue is with the bias pot's. They are kind of unusual in a single tube preamp config, but hey, it is SWR
Click to expand...

The bias pot should have nothing to do with a single tube preamp in an amp with a solidstate power amp. :confused: The bias pot would be for the output section, right? :hmm:
 
#12
Yes, I am not an expert, but you should be correct except even the schematic for my BASS 750 shows biasing for it. Still only a single tube. That is why I am looking for a schematic for this amp so my amp guy can figure out exactly what he is looking at.
 
#13
What I was getting at is that the bias pot is to set the bias for the output stage; there is no bias pot for the tube preamp, they are generally self biasing through the cathode resistor/capacitor pair. If your tech doesn't know what that bias pot is there to do I think you need a different tech, with or without a schematic for that amp. As mentioned above, virtually all SWR amps can be figured out using any of their schematics given just how similar they all are.
 
#15
How is it so different looking? From the photos I can find (as small as they are) it looks like other SWR amps, kind of like a cross between a SM400 and a Bass 350 (no slider pots on it). Can you post large photos of the amp front and back, please? Don't let the outside fool you, though. I have a bunch of schematics that I got from SWR when I visited them in the mid '90s, they are virtually all the same, and they even mentioned that to me during a phone conversation with one of their techs, Carlos (IIRC).
 
#16
Like I said, the front looks completely different (no sliders) than the other several from around that time. I do not have the amp right now, but I will post some pics. Either way, it doesn't change the fact that I want a schematic for this amp
 
#17
Post some good guts photos, too, so we could see how different it may be circuit-wise, possibly. This amp was made way before Fender even knew SWR ever existed so i wouldn't look there. You best (probably only) hope for a schematic of that amp model specifically would be to talk to Steve or have someone examine the amp and draw one up.
 
#18
Jeff Scott said:
The bias pot should have nothing to do with a single tube preamp in an amp with a solidstate power amp. :confused: The bias pot would be for the output section, right? :hmm:
Click to expand...

Tube and solid state power amps need to be biased and the bias needs to be checked from time to time. The bias on a tube amp needs to be checked when the tubes are changed. Likewise, the bias of a solid state power amp needs to be checked if the output transistors are changed or are acting up. In both cases, the bias sets the steady state operating point of the output stage. Think of it as tuning a string to pitch.

The advantage of having the schematic would be that it should have information on how to set the bias and more importantly what the bias voltage should be. This makes servicing the amp easier. The preamp tube in this amp is self biasing and needs no attention when it is replaced.


iriegnome: If there is a chance the GT made the amp, it is worth contacting fender again to see if it is with their GT schematics or contact Aspen Pittman directly on Facebook to ask if they produced the amp and have any info. If they don't have the schematic, they may have a service note describing how to set the bias. It would be worth asking about both. Also, Aspen Pittman has a lot of schematics in his book. I have an early edition and it isn't in there. The latest is the deluxe edition, version 5. I've ordered a copy, we'll see what it has.

As a side note, the first time that I called Aspen Pittman he needed to look something up. He called back, west coast to east coast when long distance calls costed, and we spoke for over an hour about all kinds of stuff. A genuinely nice person. I wouldn't hesitate to reach out to him about this.
 
#20
beans-on-toast said:
Tube and solid state power amps need to be biased and the bias needs to be checked from time to time. The bias on a tube amp needs to be checked when the tubes are changed. Likewise, the bias of a solid state amp needs to be checked if the output transistors are changed. In both cases, the bias sets the steady state operating point of the output stage. Think of it as tuning a string to pitch.
Click to expand...

Of course, but we're talking about a tube PREAMP. ;) A tube PREAMP that has only a single 12AX7 in it. The power amp is solidstate and that is where this particular bias pot is located. ;)
 

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