Newbie quetion

[Jenkster]

Hi all, newbie to the forum looking for information.  I have an opportunity to buy a 1965 SUNN head for $400 locally.  It is in great shape cosmetically save for a small tear in the grill cloth.  The pre-amp and rectifier tubes look original, the two 6550's have been replaced.  It has a hum and plays at very low volume.  Can't seem to find much information on this year of SUNN amp.  Is it likely one the brothers built in their garage?  Any information would be appreciated.

Thanks

[Isaac]

A picture would help immensely. How do you know it's from 1965?

[Jenkster]

The funny thing is the seller had this amp listed on the local Craigslist earlier today with four very poor quality pictures.  I just looked for the ad again and it's gone.  I have an appointment to see it tomorrow morning.  The seller told me it's from 1965.  He said the amp section is a Dynaco and it has a sun with a smiley face for a logo.  He claims everything is original save for the power tubes.  If the caps are original, I'm sure that is part of the sound problems.  Any definitive way to tell the year of manufacture?

[EdBass]

I think the top control, split chassis amps are prior to '67, smiley face logo '65.

[Jenkster]

If it is a 65 and in the condition the seller claims, it is worth $400 to me.  I could tell in his pictures that it has top controls and probably a split chassis.  I let my 74 Model T go a few years ago and have regretted it ever since!  If I do get it, I will be sure and post pictures.  Thanks EdBass for the info!

[EdBass]

If it's a top control, it's a split chassis. As a rule, I don't speculate on vintage equipment value, I'm a firm believer that used gear is worth exactly what someone is actually willing to pay for it, "opinions" are worthless. I have absolutely no use for the opinion of someone without "skin in the game".
That being said; I would pay $400 for that amp as described, without hesitation.

[Jenkster]

I picked up the amp today and it appears to be original. I am having difficulty posting pictures. I'm not too computer literate! I do have a couple of questions. There appears to have been something mounted inside the cabinet on the lower right side looking at the back. It would have been approx. 6" long and 3" wide attached with four screws. The seller said there was nothing there when he aquired it. Also, for schematic puposes, can someone tell me the model of the Dynaco amp they used?

[Jenkster]

A friend of mine and I fired it up and it had a very loud HUM! Volume didn't change the level so we figured it had a ground loop.  We pulled the amp and found someone did a hack job on it. The bias cap was gone, the resistor accross the pre-amp power socket was gone, there were other gounding and wiring issues as well. The GZ-34 rectifier tube was replaced with a 5U4 and there was a bad pre-amp tube, a 12AT7 instead of a 12AX7! I think that's it. Oh, the amp power cord was replaced and instead of a 3 amp fuse it had a 32 volt 4 amp fuse! I'm not quite sure how it worked at all???

We did cure the hum but the volume is too low? It blew the the 3 amp 250 volt fuse we put in after about 10 minutes of operation. It is certainly a work in progress! For the time it did play, it was very, very clean!

The pots and filter caps are dated Jan/Feb of 1966. The pre-amp housing was obviously "home made" by the uneven sharp cuts on the aluminum sheeting. Looks like they used tin snips or something similar to cut it, how cool is that! The pre-amp appears to have been un-touched inside. Sure was a pain in the a** getting it out of the cabinet! Pots are noise free which is a good thing.

I am still trying to reduce the resolution of my pictures but have had no success. Hopefully I can get my daughter to help me with that in a couple of days.

Any input would be appreciated!

Thanks,

Mark

[Jenkster]

I suppose it would be an exercise in futility locating a schematic for the pre-amp? If anyone knows the type of screw-in bulb it takes, that would be helpful.

[JoeArthur]

I suppose it would be an exercise in futility locating a schematic for the pre-amp? If anyone knows the type of screw-in bulb it takes, that would be helpful.

Psst... sell it to EdBass!!!

[EdBass]

I picked up the amp today and it appears to be original. I am having difficulty posting pictures. I'm not too computer literate! I do have a couple of questions. There appears to have been something mounted inside the cabinet on the lower right side looking at the back. It would have been approx. 6" long and 3" wide attached with four screws. The seller said there was nothing there when he aquired it. Also, for schematic puposes, can someone tell me the model of the Dynaco amp they used?

It's a Dynaco Mk III (KT88/6550) or Mk IV (EL34) power amp and a (mostly) PAM preamp. I wasn't aware that Sunn amps that old had a reverb tank, but that could explain the "missing piece". Do the controls make any mention of reverb?

[EdBass]

I suppose it would be an exercise in futility locating a schematic for the pre-amp? If anyone knows the type of screw-in bulb it takes, that would be helpful.

Psst... sell it to EdBass!!!

I assume you are being smug Joe  . All kidding aside, I would be a player if it's not too hacked up. It's not like they are making any more of them.

[Jenkster]

Thanks for the reply. I did figure out it was a Dynaco Mark III and matching pre-amp. There were issues with the amp that have mostly been cured. Naturally I have kept anything that was removed. Whovever worked on it before removed the bias cap but didn't replace it? That was just one issue. No indication of reverb just the volume, bass and treble pots, high, low, standby and power switch, single 1/4" input. Since I can't seem to reduce the resolution of my pictures, I may be able to e-mail them to someone if interested in checking it out. At this time, it is not for sale.

[JoeArthur]

I suppose it would be an exercise in futility locating a schematic for the pre-amp? If anyone knows the type of screw-in bulb it takes, that would be helpful.

Psst... sell it to EdBass!!!

I assume you are being smug Joe  . All kidding aside, I would be a player if it's not too hacked up. It's not like they are making any more of them.

Nope, I never "be smug". I can't even think of how I would start! 

Yep, they are not making any more of a lot of things...