Hammond AO-58

[DummyLoad]

hammond OEM the dynaco ST-70 amps. they are P2P wired ST-70 with a single 8 ohm output tap on the OT. used in tone cabinets. i did not know this. cool amp and hammond P2P wiring quality...


see one here for a short time...

[sluckey]

Looks like you and I are following some of the same searches on eBay.   

You may also find this interesting...

http://www.ebay.com/itm/Hammond-AO-59-dynaco-mark-iii-KT88-mono-block-tube-amplifier-hi-fi-organ-guitar-/182562048699?hash=item2a818bcabb:g:ffcAAOSwX61ZBjOa

[sluckey]

Here's a little info...

http://dynacotubeaudio.forumotion.com/t2654-the-hammond-ao-58-1-a-hard-wired-dynaco-st-70-clone-from-the-1960-s

[Ed_Chambley]

This is where I I got mine. I got one of the tone cabs just for hauling it off. The Leslie made the Hammond cabs not desirable. They also have nice speakers in them.

[DummyLoad]

Looks like you and I are following some of the same searches on eBay.   

yes, yes we seem to be!

the transformers mentioned in that linked thread state they were hammond wound - i don't think that is the case, they have a date stamp and the EIA code is 218 which is jefferson electric: they made transformers.

hammond used silicon in the bias supply - better than selenium.

cool spin on the MKIII too. would be nice to find a pair unmolested for a reasonable $$.

--pete

[sluckey]

I prefer the looks of the PTP wiring rather than the PCB. I was always nervous about tube sockets mounted on fragile phenolic circuit boards.

[DummyLoad]

I prefer the looks of the PTP wiring rather than the PCB. I was always nervous about tube sockets mounted on fragile phenolic circuit boards.

concur: the PCBs from that era were too fragile and unreliable.

i scrapped out my ST-70 - it was/is a rust bucket. i attempted to revive it with a new production board that was designed to accept 6AN8 but then discovered that the power tube sockets were shot and the builder cut the transformer leads too short to begin with. the solder joints were 90% crap. so i stripped it in frustration, lost interest and then shelved it. still have the iron and the chassis - i gave the replacement PCB away for another restoration. someday i may clone a sun amp.


--pete

[PRR]

> fragile phenolic circuit

In-the-day, I maintained ST-70s on salary. Not that they were fragile, but the old stuff in the Dynaco chassis "toasted" badly. I don't know how any survived. It is clear why ST-70 replacement boards (and circuits) are everywhere.

Modern fiberglas PCB would last forever in a ST-70. But they were what they were: early low-price PCBs. And we didn't mind much, because Dyna was coming out with better stuff (the wretched transistor amps, which wouldn't burn a PCB much but in hard use did eat transistors).

[DummyLoad]

burn a PCB much but in hard use did eat transistors

nothing like the phase (fry) linear 400 or 700 amps though: pure junk.

what i meant by fragile is that the traces pop off the phenolic with the second or third re-heat. just junk.

--pete