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Hammond AMPS, AO-43

kb8dns

kb8dns

pulled into the vacuum!
Received my second Hammond amp today, a win from EBAY. This one is in good shape. Replaced a couple of caps as one had a blowout... see pic.
Sound good through my ATSs right now! :music: The first one is a recovery from the scrapper, a little bent but just fine and the tubes made it A-OK!
Thinking of how "industrial" they look I may rebuild them into a Stereo single chassis with wood sides and less on the deck. :scratch2:
Since the input are lacking controls I am using my puter for a source, playing mp3 files and making use of the equalizer and other computer controls, for now.
Did not use the first tube, a 12BH7A, as there is already two 12AX7s as first stages. I think the first tube was used for a preamp for the reverb in the organ.
Just wondering if I can use just one of the power trannys and rectifier tubes, I think one is enough as it powered several other electronics in the L-122 organ. :thmbsp:
 

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I've been watching these show up on 'bay for a while. They would make better guitar amps than hi-fi amps, and I wanna get some to clone into 18 watters. They even have a nice tagboard already! That output tranny looks strikingly similar to a deluxe reverb's, and the power transformer is shielded. Tell me, do the EIA codes on the transformers start with 606?
 
Thespeakerdude8 said:
I've been watching these show up on 'bay for a while. They would make better guitar amps than hi-fi amps, and I wanna get some to clone into 18 watters. They even have a nice tagboard already! That output tranny looks strikingly similar to a deluxe reverb's, and the power transformer is shielded. Tell me, do the EIA codes on the transformers start with 606?
Click to expand...

The codes do not begin with 606 but here is what is on them....

First amp, power trans- 003-024157 549-7003
output trans- 003-036550 524 69

Second amp, power trans- AO-24157-1 549-6749
output trans- AO 24158 0 524 68 20

I think you are correct on saying that these would make good guitar amps and if you think about it... just disconnect the organ and plug a guitar in! :thmbsp:

I am using them for audio for now as I am "working" my way into tube audio and these Hammonds sound better than any SS I have heard. A "fuller" OPT would be better for audio and I think the 6BQ5s are thin sounding, sort of... My two EICO HF-20s will do better for me... :music:
 
I wouldn't try to run both channels of output stage from one power transformer.

I have an L110A... same basic organ. The only other tubes running from the power supply are three small tubes in the upper preamps (12AU7 and 12AX7 types). Those only draw a couple of milliamps per section... maybe 20ma for the whole bunch. The 12BH7 on the amp itself might draw another 10ma, max... so, that's only 30ma you would be "liberating" for the other channel.. plus, a few milliamps would be needed for the DRIVER tube... that only leaves, maybe, 25ma for the outputs.

Given that EL84/6BQ5 outputs need between 70-90 milliamps for a PP pair... that's quite a deficit.

There's also the heater considerations... a pair of EL84s need 1.5 amps (.75 per tube). The three tubes you're taking out (from the upper preamp) are only going to "liberate" about .9 amps. That's still a .6 amp "overload".

Mind you, I would expect it to run for a while... but you'd probably be in danger of eventually taking out the power transformer, on that much load...

Regards,
Gordon.
 
I would gut them and rewire them for guitar amps, they aren't much good for that with the stock wiring. I believe the 12BH7 is the reverb driver. I bet it would make a nicer one than a 12at7 too, with its higher current capability.

549 is midwest coil company. 524 is triwec, never heard of 'em. Don't get me wrong, they would make some sweet monoblocks if you wanted to go that way, but probably would require a rewire to a better circuit and removing a lot of frequency shaping networks in there. That OPT looks nice enough sized to pass for Hi-Fi, and if the 6bq5's are original hammond labels then they are most likely made in Holland amperex's. Try increasing the size of your coupling caps and you will get better bass response.
 
GordonW said:
I wouldn't try to run both channels of output stage from one power transformer.
Given that EL84/6BQ5 outputs need between 70-90 milliamps for a PP pair... that's quite a deficit.
There's also the heater considerations...
Mind you, I would expect it to run for a while... but you'd probably be in danger of eventually taking out the power transformer, on that much load...

Regards,
Gordon.
Click to expand...

Thanks Gordon, Just what I was looking for concerning the power supply, if I do revamp them together as a stereo unit I will use both PTs as the supply... Anyway the more lit tubes the better! :D
This affair has proven to be a boon for me as a learning lesson and eyeopener!

Rod
 
Thespeakerdude8 said:
I would gut them and rewire them for guitar amps, they aren't much good for that with the stock wiring. I believe the 12BH7 is the reverb driver. I bet it would make a nicer one than a 12at7 too, with its higher current capability.

549 is midwest coil company. 524 is triwec, never heard of 'em. Don't get me wrong, they would make some sweet monoblocks if you wanted to go that way, but probably would require a rewire to a better circuit and removing a lot of frequency shaping networks in there. That OPT looks nice enough sized to pass for Hi-Fi, and if the 6bq5's are original hammond labels then they are most likely made in Holland amperex's. Try increasing the size of your coupling caps and you will get better bass response.
Click to expand...

I do not have much invested in these as one I recovered from the scrap iron pile and the other I won on EBAY. So all in all they are the experiment for me to learn more about audio tube amps. I won a second one on EBAY but that is for a friend who wants a 18 to 20 watt amp for his guitar, he has a SS now. Might be a swap out or a build out for him.
Either way it is going to be fun! yes... one hand in the pocket too! :nono:
 
AO-43 Hammond Chassis

I got one of these from a friend of my brothers. I was originally going to turn it into a Matchless Lightning clone (Ceriatone layout and get the parts missing from them). I can solder well and follow directions, but I don't know enough about identifying the wires on the transformers and whatnot quite yet. I am really wanting to turn into a Marshall 18watt -as those are some of the best guitar tones to my ears.

Can someone help point me to a place online (I am strapped for disposable income right now) that guides one from input jack to loudspeaker, explaining the various components, how and why they are used, etc.?

Even point to a comprehensive book I can buy.

Thanks a bunch, and please forgive me if I have posted a redundant question -I haven't found this specific question(s) asked.
 
those amps are for the reverb channel driving a 8" speaker ( i think 8 ohms).
I have a pair of the el84 amps and the latter ecl86 amps.
Haven't gotten around to doing anything with them but there was a pair for sale here already modified for a good price.
 
Im a bit late to this shin-dig, but figured this is w adding to the pile. When hooking these monoblocks up use an RCA splitter and input one channel to white and the other to the black input. (The two inputs right next to each other) t worked wonders for me. Hasn't caused any issues so far with what ive hooked it to. These little guys pack alot of punch. Enjoy
 
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