50's Ampeg Schematic needed

[archbishopbenny]

I just picked up an old Ampeg 7030 New Yorker amp. It appears to be from 1958 and is essentially the same amp as the 6030 Continental Duette Guitaramp. It seems to be a pretty rare one as there isn't even a picture of it in the Ampeg Story Behind The Sound book.
The amp is missing the original back panel and is therefore without a schematic. If has one or knows where I can get one it would be appreciated.

[Rob Mercure]

ABB.

I wish I could help you - but hopefully someone will know this rare bird. Could you post pics of the amp - as many angles as you feel comf ortable (but especially the front) - I don't know about anyone else but I'd really like to see the beast.

Thanks

Rob

[archbishopbenny]

Here are a few pics Rob. To the best of my research this amp is properly referred to as the 7030 New Yorker Accordiamp. It's 35 watts with a 15" Jensen P12N speaker. As you can see it's in pretty rough shape cosmetically, but is apparently in perfect working condition on the inside. The back panel has been misplaced and/or removed over the years and a new one has been fashioned. I'd like to try to find out what the original back panel looked like so that I could have one made as I'm pretty sure it wasn't quite as closed as this one. There's also been a grounded 3 prong plug added as well as a polarity switch. This is one of the early style Ampegs when they were modular with separate preamp and poweramp chassis. Ampegs of this period usually had one channel with a 6SJ7 Pentode preamp while the other channel had a 6SN7 twin-triode preamp. Mine has the 6SJ7 scribbled out on the tube compliment chart inside the cabinet, it's been replaced with a 6SN7. I may have that one channel changed back to the 6SJ7 if possible as it would be nice to have two different channel sounds. Also most Ampegs of this vintage have an OC3 voltage regulator tube for the power tube screen supply that yielded more headroom. Mine doesn't have this tube but I can see there's a hole in the poweramp chassis where another tube would fit. If I can find a schematic I may have the circuit modified to accommodate this as I play jazz and like the idea of this extra headroom...not that the amp doesn't have a lot of clean headroom. I've already used it on a gig and a jam session and it sounds great! Very fat, quite dark, very warm, very 50's jazz guitar...just what I was looking for!! That being said, I'm sure it could sound even better since one of the output tubes was broken during shipping (thanks again UPS) and I had to pop another 6L6 in, therefore the output tubes aren't matched. Anyhow, have a look. I think Ampegs of this vintage are very special, especially if you're looking for a certain type of sound. And if anyone out there has a schematic for this or any other information for the matter, don't hesitate to let me know.

[Rob Mercure]

ABB,

Thanks for the pics - nice. I can't tell from your response exactly but I'd recommend keeping the amplifier stock rather than modifying it. I know it's your amp and you've got a sound you're after but the machine is a rare piece of history and there probably ain't many left.

Ampeg as you probably know started out making products for bass guitars (pre solid body) so you amp was probably designed as a bass amp. So, as to your back panel, all of the vintage Ampeg bass combos I've worked on/seen had a closed back panel - but with the power sub-chassis in the bottom I expect there were some ventilation holes there...???

Using an OC3 on the screen grids of the output tubes would hold the voltage at 105 volts - this is so low that the tube charts don't show it. I'm pretty sure that there was probably more to the regulator circuit but 105 V on the screens would drop your power output so low you'd hate and I don't associate regulated screen output tube voltage with "head room" - if anything I think it would limit it a bit. Now I seem to remember some past discussion on the Ampage forum which preceeded this one about regulated preamp supplies and headroom - but I'm fuzzy on this one. Anyhow it might do you good to search the archves on this - 105 volts for a preamp supply is "ball park."

If you find a schemo please post it.

Thanks

Rob

[Rob Mercure]

OK, I'm wrong about the OC3 - checking some other schemo's determined that the regulated voltage for the screens would be adequate. Still not sure that this would translate to "head room" - need other's opinions on this but I still recommend not making any alteration that can't be easily returned to stock. But when I see an old chopped hot rod go down the street what I see inside my mind is another piece of history probably destroyed forever IMHO.

Hope you find the schemo.

Rob

[die Bullen]

I know this thread is very old, but....

OP I have one of these amps that is coming into my possession at the end of this week but I also do not have the schematic- however I do have the original back panel shot if you want it.

A correction- this amp is a duette continental but voiced for accordion in the tone stack, it was not intended as a bass amp. The 15" speaker you have was absolutely top of the line for Ampeg in the 50's- the 35 watts of output and the very large tube complement is further evidence of this. This is a very special amp- I hope that you did not get rid of it.

6SJ7 is also scribbled out on mine on the ch1 tube chart- I think this was an error and the 6SN7 was always intended in this spot. As far as the 0C3 tube goes- what did they mod to remove this tube from the circuit? Mine definitely has the 0C3 tube

dB

[archbishopbenny]

Glad to hear from you, dB. This amp has been sitting in the back of my closet for quite a while. I fire it up once in a while but I usually play through a 1965 G-12. I would actually prefer to get this one up and running as I really do love the 50s Ampeg sound. That back panel shot would be greatly appreciated. If you could provide me with measurements that would be great too...I'm particularly interested in getting the porting on the back correct as I'm quite sure the circular holes that are on the makeshift rear panel of mine are nothing like the original. I agree with you that it's a very special amp. Regarding the 6SJ7, at least according to the info from the Ampeg: The Story Behind the Sound book, many of the two channel Ampegs produced in the 1950s had different preamp circuits in order to have two different sounding channels (see my 06-08-2008, 11:23 PM post). As for the OC3 tube not being present in mine, I don't know if it's a mod or if that's simply how my amp was when it left Ampeg in 1958. From what I've read these were all still essentially handmade amps at the time, during the late 50s, and there was considerable variation between amps of the same model number. By the way, I'm just a player and I really know nothing about electronics so I'm probably a little weak on understanding exactly what has been done to my amp.

BB

[die Bullen]

responded to you over on vintageamps- let's keep that one going- no need for 2 threads!
dB