Restoring a Solarus

[sonicmojo]

Hello Sunn friends!

I am brand new to the forum and just looking around for the first time. I am in the midst of restoring a '68 Solarus that I recently came across (rusty chassis and no transformers). I have an identical working specimen to compare with so I have some help there. I thought I'd drop by and say hello. I'll post my progress. Mine is the top picture.

If anyone has a source or DIY spec for the SM-1 Optotrem module, please let me know. I'll sort something out but any help is appreciated.

Thanks,

Bryan

[sonicmojo]

Success! After doing a lot of chassis cleanup and installing some new caps, the multi-cap can, transformers, etc., I've got it working strong! At the moment I have to jumper the tremolo circuit as it is missing the Optotrem module but I plan to work on making my own replacement next. I'm getting a nice blinking LED across the leads so I think I can figure out my own solution using some radio shack photoresistors in combination with a suitable LED. I'll have to experiment.

[Soundmasterg]

Amp is looking nice!

I was talking to Conrad last week and he mentioned to me that back in the day Sunn made their own Opto trem modules, so it sounds like creating your own today is the right approach as you will never find a direct fit unless it is from another old Sunn amp.

Greg

[sonicmojo]

After some experimenting, I found that a green LED and a Radio Shack photocell work pretty well. I used the smallest photocell in the pack that RS sells. The smallest photocell offers the most dark resistance, about 400k. I made a bug with shrink wrap tubing.

I may try a Vactec Valtrol sometime but I like the way this is working.

I'm building the cabinet now. I found some SUNN tolex and corners on eBay. I still need similar grill cloth, handle, and a nameplate. I'm trying to get this as close to original as possible but it won't be exact.

Also, I found that the Gibbs reverb used in 60s Fender solid state reverb units and Hammond organs has the same "1122" marking as in the Solarus I have to compare to. Those are fairly readily available on eBay. This may be helpful to anyone trying to fix their reverb.

[sonicmojo]

Well I worked out all the bugs in the amp and it is sounding good. For some reason the grounded lug of the Volume pot was wired to the grounded lug of the Contour pot in the design of this amp. For some unknown reason, this was causing a ground loop in my amp due to different ground points off these separate pots. If anyone else encounters a 60 Hz hum in their amp, they might consider disconnecting this wire as it seems to serve no real purpose. I built the cabinet for it and got some of the "similar" grill cloth from Acoustical Solutions from Richmond, VA as posted on this forum by someone else. It is not exactly the same but close as I'm going to probably get. I did manage to find some SUNN Tolex and corners. I still need a amp plate badge. 0-10 knobs would be nice too. Also pictured with my '68 restore is my '71 Solarus.

Aloha from Oahu!

Bryan

[sonicmojo]

I gave up on finding any real amp logos so I made my own SUNN badges for my two amps that are missing them - printed matt 100lb matte paper and mounted on some scrap circuit board material. It's not exactly right but good enough. I'll spray with some satin clear coat and be very careful drilling holes to mount.

Total cost: $1.00 for the printout at a print shop.

[sonicmojo]

For those in need of a tremolo bug in the older SUNN Solarus models, the Vactrol VTL5C9 works pretty well.

http://www.mammothelectronics.com/VTL5C9-p/400-1109.htm

[BassHog]

So, no problem at all with that Vactrol? I'm sure a bunch of folks around here would love to know that they work well in the amp.
You said "Pretty Well" does that mean not exactly perfect?

[sonicmojo]

So, no problem at all with that Vactrol? I'm sure a bunch of folks around here would love to know that they work well in the amp.
You said "Pretty Well" does that mean not exactly perfect?

Bottom line is you can get deep tremolo pretty well but not subtle tremolo that easily. I'd call it choppier than a Fender or Ampeg. I tried the  VTL5C8 also but it was very weak compared to the VTL5C9.

Here are my observations:
I've cycled through a few of these Solaruses lately and it seems to work pretty well the same as the others I have tried which is it doesn't really come on until about 5 on the Depth dial and can be a bit choppy at low settings and hard to dial in just a subtle tremolo. Turn it up and it gets pretty deep though. There is not a lot of pulse clicking going on but you can hear it a bit, especially if you have reverb on a higher setting. I won't say it is better or worse than a DIY LED and photoresistor but I haven't tried all LED colors. I'll probably experiment some more. I'd really like to get a more subtle tremolo on the lower Depth dial (1-5) but I haven't gotten there yet. I've swapped electrolytics on the board but have not gone as far as trying different transistors. Hope this helps explain.

Maybe someone else can chime in on how their stock Solarus behaves, especially with lower depth dial settings.

[patlaw]

Here is information about the photocell from another forum:

The Silonex NSL-5160 photoconductive cell has the same or similar properties as the custom cell in Sunn amps. The bulb used with the cell is probably a 6v grain of wheat bulb.

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