Hammond AO-43transformer information needed

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zappacat
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Hammond AO-43transformer information needed

Post by zappacat »

Does anyone have a schematic for the AO-43 chassis/amplifier. I'm trying to find out the values for the power transformer and output transformer leads assuming they are working properly. Here are the numbers on the components that I need information for.

AO-24157-1 549-6623
AO 24158 0 524 66 12
AO-24159-0 549-6621

Any help greatly appreciated.
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NastyOldTech
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Post by NastyOldTech »

The power transformer is something like 315VCT. The secondary for the rectifier filament has to be 5V with at least 3mA for that 5U4. Tally up the tubes and you'll get an idea of the total heater current running at 6.3V. I would guess that iron could take more. It's also shielded.

The output is push pull and they have EL84's with a 8 ohm load. Your primary is likely to be in the 8k neighborhood with an 8 ohm load.

That other one's some sort of choke, in the reverb section?
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Freddy
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Post by Freddy »

I think that AO-43 chassis is from the early L-100 organ amp not the later L-100 which is AO-47. There should be a schematic link somewhere on the net. It will at least give you an idea of the speaker load used with the output transformer and maybe power transformer voltages.
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Re: Hammond AO-43transformer information needed

Post by gh1 »

zappacat wrote:Does anyone have a schematic for the AO-43 chassis/amplifier. I'm trying to find out the values for the power transformer and output transformer leads assuming they are working properly. Here are the numbers on the components that I need information for.

AO-24157-1 549-6623
AO 24158 0 524 66 12
AO-24159-0 549-6621

Any help greatly appreciated.
This is what I've either found listed or actually measured myself...

AO-24157-1 549-6623 - power transformer
315VCT - 160mA (I've also seen it listed as 135mA)
6.3VCT - 4A? (tubes in the organ = 4.37A)
5V - 3A
Manufactured by Midwest Coil & Transformer in the 23rd week of 1966

AO 24158 0 524 66 12 - output transformer
7.2K primary
8 ohm secondary
Manufactured by Triwec Transformer in the 12th week of 1966

AO-24159-0 549-6621 - reverb driver
10H - 75mA - 500 ohm
Manufactured by Midwest Coil & Transformer in the 21st week of 1966
Last edited by gh1 on Fri 06/11/10 8:41 am, edited 1 time in total.
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Re: Hammond AO-43transformer information needed

Post by zappacat »

gh1 wrote:
zappacat wrote:Does anyone have a schematic for the AO-43 chassis/amplifier. I'm trying to find out the values for the power transformer and output transformer leads assuming they are working properly. Here are the numbers on the components that I need information for.

AO-24157-1 549-6623
AO 24158 0 524 66 12
AO-24159-0 549-6621

Any help greatly appreciated.
This is what I've either found listed or actually measured myself...

AO-24157-1 549-6623 - power transformer
315VCT - 160mA (I've also seen it listed as 135mA)
6.3VCT - 4A? (tubes in the organ = 4.37A)
5V - 3A
Manufactured by Midwest Coil & Transformer in the 23rd week of 1966

AO 24158 0 524 66 12 - output transformer
8 ohm? (two 12's @ 15.5 ohm plus one 4" @ 4.4 ohm all in parallel in the organ so ?)
Manufactured by Triwec Transformer in the 12th week of 1966

AO-24159-0 549-6621 - reverb driver
10H - 75mA - 500 ohm
Manufactured by Midwest Coil & Transformer in the 21st week of 1966
Thank you very much for this info. Have you built something with this amp/chassis?
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gh1
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Post by gh1 »

I built a lite 2b as a gift for an uncle that got me started playing guitar as a kid. I'm working on a superlite right now for my oldest son. Still have another that will become a clone of an amp unrelated to this site. And a 4th that ended up getting auctioned off recently to keep the wife from having a nervous breakdown.
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Post by Shottky »

The output transformer that came on my AO-43 was 8 ohm output, 7100 ohm input. However, the listing of two 15.5ohms in parallel with one 4.4 ohm would lead to an output impedance of 2.8 ohm.

I used the standard 6.3V test on the output leads and measured the voltage on the input leads, did the math, and got the 8/7100 result. It matched up to what I saw when I was testing a 125E.

Serial number:
A0 24158 0
524 63 31



The specs for the PT and choke were exactly as gh1 had.
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gh1
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Post by gh1 »

I figured the OT was 8 ohm output. I used it with a single 8 ohm 12" speaker with no issues.
Last edited by gh1 on Sun 04/18/10 9:40 am, edited 1 time in total.
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Post by Shrapnel »

One way to know for sure.

input some voltage, measure THAT voltage, and the voltage out.

(i.e 6.6v on sec, 131.5v on anode/plate leads)
do the math
(131.5/6.6)^2:1

(131.5/6.6)^2 * Speaker Impedence (say 16 Ohm)

about 6300 Ohm Primary (within 10% of 6600 Ohm P-P impedance)

Tests relatively good (Final test is to put audio through it.)

[ My numbers aren't exact here, but make sure you substitute your own numbers in for your results ]
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Post by NastyOldTech »

Using this formula I tested a AO-43 OT today. Part #AO-24158-0 and I got about a 7K primary @ 8 Ohms load.
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gh1
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Post by gh1 »

Sorry to bring up such an old post, but I've run into this again and I'm still confused about that 4" speaker. I completely agree that the OT is somewhere in the 6.6K - 7.1K range. Does the cap confuse the math or am I just missing something?

Image
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Post by guitar-rocker »

It makes an ok LiteIIB, heater voltages tend to run high due to the transformer windings were set up to run voltages in the past of @ 117 volts, and the 315-0-315 primary is a tad hot too. Mostly people subvent around the higher B+ by using a 5Y3 in this Hammond.
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Post by zaphod_phil »

Don't worry about the 4" speaker fed via a cap. It's a tweeter, and the cap ensures it only gets high frequencies fed to it. So you just get rid of that speaker and cap, since tweeters are highly undesirable in guitar amps.
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Post by POWDOG »

I've made a bunch of TMBs, AC15s and 2061s using the AO-43 as a donor. I usually gut the amp, leaving the big dropping resistors underneath the vent (64, 300 and 1500 ohm) as wired in the schematic. With a 5U4, this puts around 340v on the EL84 plates, which is Hammond spec. A little hot, but haven't burned up any tubes yet. And I think the OT's on these sound fabulous.
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Post by Patrick620 »

Try http://www.captain-foldback.com/ for Hammond schematics
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