ebartlet's Mixer rebuild project: Power supply

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ebartlet

Well-known member
Joined
Jun 5, 2004
Messages
179
Location
Nashville, TN
I'm replacing the 4558's with 5532's, 70 of them! I would like to avoid building a new PS, to save $. According to the spec sheet, 4558's draw 6.6ma max and 5532's draw 16ma max.

Max current draw stock on the +16.5/-16.5 supply is estimated to be about 0.5A After replacing the IC's, I'm estimating a current draw of 1.4A

I beleive that the transformer and most of the regulator circuit might be up to the task.

Here is the schematic:

http://www.ericbartlett.com/images/tapco_c12_power_supply.JPG

I do not have any other trannies to compare with, but here's what I know:
Height=2 3/4" width=2 3/4" length=3 1/4" stack height=1 1/4"

The 30 - 0 - 30 windings measure 26 - 0 - 26 and 1.35/1.35 ohms.

Can anyone give me an estimate on the VA rating? I tried to calculate but I don't think I came up with an accuarate number (not even close!?!)

The other two windings are for phantom power and meter lights (4).

Here is what I think I should replace:

-1N4002 diodes in bridge with something bigger
-R9-12, R27-30 Need higher power dissapation
-Upgrade filter caps

The TIP41 (Q4) and TIP42 (Q10) pass transistors are good for 6A max.

Any thoughts, hints or suggestions?

Thanks
 
I think the 4558 are what people use to build replica Ibanez tube screamers. If so you might want to look after these as they seem to go for ridiculous money on ebay , particularly if they are the Texas Instruments version
 
Isn't it the JRC4558 that all the tweako-heads are after?

I think a wholesale replacement of ICs in a mixer is a bad idea without trying one channel first to gauge the improvement, if any.
 
[quote author="NewYorkDave"]I think a wholesale replacement of ICs in a mixer is a bad idea without trying one channel first to gauge the improvement, if any.[/quote]

I would agree, I have one channel out and ready for the swap once the parts get here, before I go crazy doin everything else.

I have a couple of weeks before things get really busy, so I'm tryin to plan ahead, so if I do like it, I can start slingin solder and wrap it up before I get too busy to mess with it for a while.
 
Do you need to replace all the IC's with the 5532? Are there places... maybe interstage, that could use a lower current JFet type IC?

Have you considered the additional heat generated from the 5532? The 553x parts when clustered together can really put out some heat.


Vince Poulos
Speck Electronics
 
[quote author="Vince@Speck"]Do you need to replace all the IC's with the 5532? Are there places... maybe interstage, that could use a lower current JFet type IC?

Have you considered the additional heat generated from the 5532? The 553x parts when clustered together can really put out some heat.


Vince Poulos
Speck Electronics[/quote]

I'm going with the 5532 because it will drop in without any modification to the surronding circuitry and it sounds good.

There is plenty of room on the PCBs and plenty of room inside, its a 25 year old mixer, the parts aren't close together like nowadays.

Thanks


So what about my power supply questions?
 
Isn't it the JRC4558 that all the tweako-heads are after?

Jeez, I think I have a bunch of those around here somewhere. I found a bunch of AD711s - are they particularly good for anything?
 
> I beleive that the transformer and most of the regulator circuit might be up to the task.

It's a cheap mixer. Why would they give you a power system 3X bigger than you really need?

Also the regulators will fold-back at 0.76A, and I bet the heatsinks are barely big enough. And the transfomer will probably suck over 1A on the IC-supply winding.
 
[quote author="PRR"]> I beleive that the transformer and most of the regulator circuit might be up to the task.

It's a cheap mixer. Why would they give you a power system 3X bigger than you really need?

Also the regulators will fold-back at 0.76A, and I bet the heatsinks are barely big enough. And the transfomer will probably suck over 1A on the IC-supply winding.[/quote]

Ok, Ok, maybe a bit too much wishful thinking...


What did you mean by the regulators folding back?
 
[quote author="PRR"]> I beleive that the transformer and most of the regulator circuit might be up to the task.

It's a cheap mixer. Why would they give you a power system 3X bigger than you really need?

Also the regulators will fold-back at 0.76A, and I bet the heatsinks are barely big enough. And the transfomer will probably suck over 1A on the IC-supply winding.[/quote]

Is the current limiting controlled by Q7 and Q11?
 
JRC4558s are used in orig. TS-9 distortion pedals. very sought after. :guinness: homebrewers pay a few bucks each for the originals.
if you put em on ebay they'll probably sell.

sleeper
 

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