Replacement for E1A606-724 / 2-24b power transformer

[nosaj]

Everything you need is in the schematic.
nosaj

[glebert]

If I could make a suggestion, I would bet that there are many similar Randall amps out there that can be had for very little $$. Perhaps one of those would be a good starting point for a clone.

[J M Fahey]

It supposedly runs at 24v 40va, which powres the amp which runs at 150 watts overall so I’m not sure what is going on.

No.
That amplifier uses +/-40V rails, so transformer is 28+28VAC.
The 100W one probably uses a 150VA transformer, so some 3A winding rating, and the 80W one around 100/120VA rating, so 2A.

You can build the preamp on perfboard or stripboard but the power amp will be unreliable, high currents are involved, you will need a PCB.

FWIW my first commercially successful MI amplifier was an Ampeg BT15 preamp built on stripboard , straight from Jack Darr´s book, driving a 100W "Tiger" amplifier, straight from Popular Electronics pages.
Worked like a charm, sold dozens or maybe even over 100 of them.

I suggest you get a 50-100W amplifier , kit or assembled, or even an LM3886 based one, all with the proper power supply, build the Preamp from Hell which is a killer project, and use it to drive the power amp.
You can get the +24V or so preamp supply from the main power amp supply.

It will be KILLER sounding, 90% of the Randall sound but in a practical to build way.

Trying to clone the full original one will be frustrating, lots of "non Electronic" problems to solve: PCBs, chassis, front panel, cabinet, power transformer, etc. .

Build this killer project first, you are wasting nothing, great practice or live use amp, experience will help you a ton with the following build.

[Shrimpfarmer89]

No.
That amplifier uses +/-40V rails, so transformer is 28+28VAC.
The 100W one probably uses a 150VA transformer, so some 3A winding rating, and the 80W one around 100/120VA rating, so 2A.

You can build the preamp on perfboard or stripboard but the power amp will be unreliable, high currents are involved, you will need a PCB.

FWIW my first commercially successful MI amplifier was an Ampeg BT15 preamp built on stripboard , straight from Jack Darr´s book, driving a 100W "Tiger" amplifier, straight from Popular Electronics pages.
Worked like a charm, sold dozens or maybe even over 100 of them.

I suggest you get a 50-100W amplifier , kit or assembled, or even an LM3886 based one, all with the proper power supply, build the Preamp from Hell which is a killer project, and use it to drive the power amp.
You can get the +24V or so preamp supply from the main power amp supply.

It will be KILLER sounding, 90% of the Randall sound but in a practical to build way.

Trying to clone the full original one will be frustrating, lots of "non Electronic" problems to solve: PCBs, chassis, front panel, cabinet, power transformer, etc. .

Build this killer project first, you are wasting nothing, great practice or live use amp, experience will help you a ton with the following build.

juan you have shown up a few times in this quest I’ve set out on and have always had killer information I really appreciate it.

when you are talking about the pcb do you mean the power amp section I’m guessing? Could the preamp be created on breadboard and then the power amp on pcb? Or when entire thing should be pcb because of the heat transfer?

And what about a 4 amp power transformer at 150vac and 28/28v? will one amp ruin the whole thing?

[vintagekiki]

As far as I remember, Randal (RG-80) we are recently graduated.

https://music-electronics-forum.com/forum/amplification/guitar-amps/917219-adding-circuits-to-an-amplifier-head-build

If this post is well-intentioned and not spam, the best some repairman rewind your old E1A606-724 / 2-24b power transformer

[nosaj]

As far as I remember, Randal (RG-80) we are recently graduated.

https://music-electronics-forum.com/forum/amplification/guitar-amps/917219-adding-circuits-to-an-amplifier-head-build

If this post is well-intentioned and not spam, the best some repairman rewind your old E1A606-724 / 2-24b power transformer

He doesn't have one he said he wants to build one from scratch. Not too sure on the intentions other than pumping people for information.

nosaj

[vintagekiki]

Manufacturers mark their products with a universal EIA code.
http://www.thevintagesound.com/ffg/eia-codes.html

The transformer in question certainly has the designation EIA 606-724 where the first three numbers indicate the manufacturer, and the other digits the product model. In your case, it is a Woodward-Schumacher transformer.
I did not find their home page, but judging by the voltages from the schematics for the Randall RG100ES, you can replace the transformer with the PT for the Marshall 2200 and 2098.
http://www.tubeampdoctor.com/en/mains-transformer-marshall-original-nos-used-in-models-2200-and-2098


Both amplifiers operate at +/- 40V and are designed for 100W power.
https://drtube.com/schematics/marshall/2200-pwr.gif

When choosing a transformer from another manufacturer, it is important that there are 3 terminals in the secondary.
The number of terminals in the primary is determined by the supply voltage.

[Shrimpfarmer89]

Thanks for the info.

I had done some research about the numbers and found the same thing about the manufacturing company that isn’t around anymore or has no info.

with the 30 /30 voltage running into the 25amp /200 volt diode, it will still be at 60 volts save 1.5 apparently due to the mfg info on the kbpc2502 rectifier.

do I need to find larger or smaller 6000/50 caps to take of a bit of the voltage to make it a clean 40 to run into the zener 24 to get the preamp voltage? Or can I just run the same setup as in the schematic.

[vintagekiki]

Leave the theory and compare the voltages on the schematics for Randall RG100ES and Marshall 2200. Both amplifiers (output stage) work on +/- 40VDC, ie they use PT with the same or similar VAC.
Since you do not have the original PT, a replacement PT with the same or similar VAC is used.
Provided that you are sure that the PT is defective, it needs to be replaced, without any modifications.
24VDC for preamp is obtained from + 40VDC via R6, C45 and zener.
Tip. Before release in work check status power amp (Q8 - Q16)

[Shrimpfarmer89]

Vintagekiki—

on the previous thread you helped me out with a quick fix to get rid of the two 12v lines that ran the reverb tank, which would eliminate the d and c lines from the preamp. after the diode the two 6000/50 capacitors are still needed for the amp to function even if the sections after r58 and r59 are removed?

Also I’m confused by your recommendation about checking the work status of the power amp, are you talking about the output of the transistors?

[vintagekiki]

...

C38 and C39 are the main filter capacitors in the amplifier.
Everything shown in schematic in your post # 4 do not remove, because is required for correct operation of the Randall RG100ES . Only replace defective components with correct ones.
If you are sure that the power amp is correct you do not have to check it.
And don't forget.
If you want to fix Randall RG100ES, please without unnecessary philosophizing.
Amplifier will be repaired "step by step"

Question.
Is a new PT installed in the Randall RG100ES?
What are the measured voltages at C38 and C39?

[nosaj]

C38 and C39 are the main filter capacitors in the amplifier.
Everything shown in schematic in your post # 4 do not remove, because is required for correct operation of the Randall RG100ES . Only replace defective components with correct ones.
If you are sure that the power amp is correct you do not have to check it.
And don't forget.
If you want to fix Randall RG100ES, please without unnecessary philosophizing.
Amplifier will be repaired "step by step"

Question.
Is a new PT installed in the Randall RG100ES?
What are the measured voltages at C38 and C39?

VK just remember this is a thought experiment from what he told me : He does not have any of this stuff and is pretty much trying to figure out what to buy.
This thread really doesn't belong in this area more in the design section.

nosaj

[vintagekiki]

VK just remember this is a thought experiment from what he told me : He does not have any of this stuff and is pretty much trying to figure out what to buy.
This thread really doesn't belong in this area more in the design section.
nosaj

I try to help anyone who is cooperative. If he has nothing, and he wants from nothing to make something , let him open the cards and say what he has and what he wants, and not to philosophize "what would it be like, if it were"
It goes without saying that everything has its limits. I'm afraid that this thread won't end inglorious as the previous "Adding circuits to ..."

[Shrimpfarmer89]

Nosaj he’s fine in doing that I’m probably going to build this amp.

from what the other poster was saying about pcb’s and heat I can find a website that designs pcb and draw the schematic out on a designer and have them shipped out.
there are soldanos that are put together on turret so I think I’m alright with the heat problem.

Vintagekiki-What are you trying to get at about testing the power in the output stage, are you making a general post about testing the voltages when it’s being built to ensure it works or is there another reason?

I “philosophize” because I’ve gotten half answers before, I’m asking questions because my train of thought was in making the amp without because I don’t want the entire section that powers The reverb tank, however at this point I’ll leave it in because it is apparently what is needed to power the entire amp.

[Shrimpfarmer89]

Thanks for the info I’ll ask straight questions next time and not dance around the question