NEW/OLD SOLARUS - Question - New to forum too! WOOOO HOOOOO!!!!!

[AjaxLepinski]

Hi gents!!!

I've been a long time fan of Sunn. My first amp was a Sentura II... bought it in 1977, when I was 17, with money earned while pumping gas.
Then, I sold it, along with my analog recording gear in 1998 and I'm still kicking myself for doing so.

After going through a variety of amps, Marshall, Peavey, Yamaha, Fender, Roland, Randall, Hi-Tone (Hiwatt clone that I still have and love), I just bought a Solarus!!! YEAH MAN!!!
I just love the way a cranked Sunn sounds through a pair of EV SROs... it's like heaven on Earth!!! I'm back in the Sunn saddle again!

The amp is in good condition and it only needs a new 1000uF cap (on order from Mouser).
However, someone removed the RCA connectors for the verb/trem foot switch and I plan on restoring this.

Here's my first question: There is a lone, RCA jack on the back. It has a single yellow wire that goes to a small, wire size hole, in the top of the trem PC board ... anyone know what this does????
I haven't seen it on any Sunn Amp before and I won't have a chance to hook it up to a switch until next week.

Second question: Does anyone know the bias values for a 1969 Solarus with EL34s?

Gut shot:


Mystery jack:


Glad to be here and thanks for your help!!!

[Jazz P Bass]

Welcome to MEF.

If the wire goes to the Trem board, it may be that it turns the Tremelo On & Off.
You will have to trace where it goes.

As to biasing EL34's: I would set them according to the B+ voltage.
It is not a critical setting.
Does this model have the 7199 PI tube?

Solarus.pdf

[loudthud]

The yellow wire is the tremolo footswitch. A simple switch to ground turns off the tremolo. The Reverb footswitch shorted the Reverb tank output to ground turning off the reverb.

[AjaxLepinski]

Welcome to MEF.

If the wire goes to the Trem board, it may be that it turns the Tremelo On & Off.
You will have to trace where it goes.

As to biasing EL34's: I would set them according to the B+ voltage.
It is not a critical setting.
Does this model have the 7199 PI tube?

[ATTACH]39555[/ATTACH]

Thanks for the reply Jazz P Bass!

I am guessing that the lone RCA jack is for turning the Trem On & Off, as well. I'm putting off turning the amp back on until I have a chance to install the new caps.
I was a bit baffled because, the lone RCA jack looks original, while there is also a space for the Trem & Reverb On & Off jacks where the Foot Switch opening is. Doesn't make sense that the amp would have two On/Off jacks for the Trem. Very curious indeed!

My Solarus came with a single, 7199 PI tube. As soon as I saw that, I ordered two NOS General Electric 7199's on fleaBay.... I took a hosing on the price but, I now have enough 7199s to last me into my not so far off old age!

Thanks for the link to the schematics - it's very much appreciated.
Cheers!

[AjaxLepinski]

The yellow wire is the tremolo footswitch. A simple switch to ground turns off the tremolo. The Reverb footswitch shorted the Reverb tank output to ground turning off the reverb.

Shorting the Reverb tank output to ground is awesome information!
I plan on restoring the two foot switch jacks and I had no idea how to go about wiring verb into the jacks.

I'm really glad I found this site and I'm happy that there are other Sunn fans out there.

Thanks loudthud!!!

[loudthud]

The original dual footswitch jack was phenolic and easy to break if you stepped on the footswitch cord.

[AjaxLepinski]

The original dual footswitch jack was phenolic and easy to break if you stepped on the footswitch cord.

It's surprising that a 47 year old amp doesn't have more wrong with it. Conrad made great sounding amps but, I guess better jack mounts were in order!

Do you own any Sunn amps?

[The Dude]

Welcome to the place!

On bias:

Weber Bias Calculator

[AjaxLepinski]

Welcome to the place!

On bias:

Weber Bias Calculator

Cheers Dude!
I posted the link to my favorites as I plan on rolling some EL34s to see which I like best.
Don't let anyone pee on your carpet!

[AjaxLepinski]

The caps arrived to day...yeah baby!!! If all goes well, I'll have them installed tomorrow morning and I'll post some clips.

The two, 7199s arrived eariler in the week - the one that came with the amp seems to be OK. I just figured that it would be best to buy a couple of NOS spares before the prices get too crazy.

I want to restore the foot switch jacks but, I'm going to have to fabricate a plate to pop-rivet in place (like the original). Being a lazy bastard, it could take a while so, I hope none of you will be holding your breath.

Seriously, the feedback that I've received has been invaluable. I appreciate it enough to have donated $21 to the site!

[Tom Phillips]

...I want to restore the foot switch jacks but, I'm going to have to fabricate a plate to pop-rivet in place (like the original)...

Hi Brian,
I offer the following additional information about your rear panel jacks.

I have seen both pop-rivets and screws used by Sunn to attach the connector mounting flanges to the chassis.
The following photo shows the likely original configuration of your Solarus rear panel. I think your amp originally used the screws.


As loudthud pointed out in post #6, the original dual footswitch jack was phenolic.
There appears to be an exact replacement part available at Phono Jack-Dual Panel Mount (Item: PHOJK-CH2-4) - Radio Daze LLC

The mystery jack that you originally asked about is a non-stock add on. Too bad someone drilled the extra hole in the chassis.

Cheers,
Tom

[AjaxLepinski]

Hi Brian,
I offer the following additional information about your rear panel jacks.

I have seen both pop-rivets and screws used by Sunn to attach the connector mounting flanges to the chassis.
The following photo shows the likely original configuration of your Solarus rear panel. I think your amp originally used the screws.
[ATTACH=CONFIG]39643[/ATTACH]

As loudthud pointed out in post #6, the original dual footswitch jack was phenolic.
There appears to be an exact replacement part available at Phono Jack-Dual Panel Mount (Item: PHOJK-CH2-4) - Radio Daze LLC
[ATTACH=CONFIG]39644[/ATTACH]
The mystery jack that you originally asked about is a non-stock add on. Too bad someone drilled the extra hole in the chassis.

Cheers,
Tom

Hi Tom,
Thanks so much for your post!
I agree with you... someone drilled the extra hole and it looks like the original RCA jacks were originally screwed in place.
I just ordered the Dual Phono jacks from Radio Daze and after installing, I'll remove that lone RCA jack and plug the hole.
Really glad I joined this site!
Brian

[AjaxLepinski]

With the help of Riffraff (hey Riffraff you here too!!!!) and GAB Grimespace, I was able to removed the 600v .047uF DEATH CAP.

Everything is working fine; the amp is quiet even when cranked to 10... and I didn't get any shocks.
However, the reverb has what sounds like a 60 cycle, single coil pickup hum when turned up.
If anyone has any ideas about curing the reverb hum, I'd love to hear them.

Here is a pic of the Death Cap


Here is a schematic I found - the Death Cap is located in the bottom right. I've read that most Sunn schematics are not always accurate. This one is fairly close.


Another angle of the wiring


Back of amp so you can see the power chord, extra power socket and fuse


...and the Death Cap removed and Polarity Switch disconnected.


Of course, I forgot to spray the pots before putting the chassis back in the shell!!!

The reverb has what sounds like a 60 cycle, single coil pickup hum when turned up.
If anyone has any ideas about curing the reverb hum, I'd love to hear them.

[Enzo]

Move the reverb pan around to see if it is picking up the power transformer. The output end of the pan should be as far as possible from the power transformer. May need to end to end it. Sometimes adding a metal shield over the open side of the pan helps, even just over the output end.

Pull the pan from the cab and get it as far from the chassis as possible at the and of the cables. Does doing this diminish the hum? If so it is likely picking up the tranny. But you could also have shielding/grounding problems with the cables. The footswitch cable can cause issues like hum, so unplug any FS to see. In fact unplug the pan cables from the chassis, still hum or hum less?

And remember, the reverb recovery stage runs off that low voltage DC supply, which could be hummy. That is a 22v zener, so make sure the zener is zening right. Maybe add some filtration like an extra filter cap between the two 1k resistors.

[AjaxLepinski]

Move the reverb pan around to see if it is picking up the power transformer. The output end of the pan should be as far as possible from the power transformer. May need to end to end it. Sometimes adding a metal shield over the open side of the pan helps, even just over the output end.

Pull the pan from the cab and get it as far from the chassis as possible at the and of the cables. Does doing this diminish the hum? If so it is likely picking up the tranny. But you could also have shielding/grounding problems with the cables. The footswitch cable can cause issues like hum, so unplug any FS to see. In fact unplug the pan cables from the chassis, still hum or hum less?

And remember, the reverb recovery stage runs off that low voltage DC supply, which could be hummy. That is a 22v zener, so make sure the zener is zening right. Maybe add some filtration like an extra filter cap between the two 1k resistors.

Hey Enzo!!!
Thanks for the input - I appreciate it. The extra cap between the two 1k resistors sounds like a great idea.
I'm not an electrical engineer and this is my first project amp so, can you suggest a cap rating?

The reverb didn't hum until I removed the Death Cap. Rifraff suggested jumping the red/white (neutral power) wire at the On/Off Switch to the PT's red/yellow wire ground point (where the Death Cap once grounded to the chassis). I'm going to try that tomorrow. If that doesn't work, I'll try the extra cap by between the 1k resistors.

Thanks again!