Aragon 4004 MK2 output replacements

[djk]

"I don't like Aragon's use of an IC chip on the amp board. IC's are hit and miss in my experience.. "

Those are not IC chips, but discrete transistors, four to a package.

 

[LiquidMids]

I'm still learning the lingo..

 

[tisegnio]

Transistors replacement for aragon 4004

I have successfully repaired a 4004mk2 that had one defect channel.
The defect channel had Toshiba 2SD424/2SB554 and the other (the working ) channel had Aragon labeled transistors.
After asking a lot of local experts from my network it seemed that several kinds (Aragon/Motorola/Toshiba) were in use throughout the lifetime of these amps.
Appearently even official repair centers allowed for one channel having one kind of transistors and the other channel having another kind.

After fruitless attempts of getting new genuine Toshibas, I settled for OnSemi MJ15003/15004.
I bought ten pieces of each and picked the ones that were closest to each other in Hfe.
These were even more closely matched than the Aragon transistors in the other channel.

Hello,
I would like to put something up here because some questions return several times about transistors of the 4004. What I know of this by now as red from an ebay page witch link perhaps you doe not know is as following:

http://www.ebay.com/gds/Classic-Aragon-Amps-A-primer-/10000000001149810/g.html

Here you can reed a statement from Mike Kusiak about used transistors of the 4004:
"The original metal case outputs [output transistors] of the 4004 were made by RCA or Motorola. Because of the great variability of the Vbe and Beta characteristics of these transistors, matching was essential. Without matching, one or more of the parallel connected output transistors would conduct all of the bias current, leaving the others off. Later, before the introduction of the MK II, Toshiba metal transistors began to be used. These were supplied by the manufacturer in sorted beta groups, which made matching much less critical... [the Toshiba metal case transistors] were also high quality, tightly matched, and designed specifically for audio amps. They were much better than the earlier RCA and Motorola outputs..."
The superior Toshiba output transistors can be identified by the name "MONDIAL" or "ARAGON" printed on the case of the transistor.


so if you find Metal cap transistors with printed Aragon or Mondial Label on an 4004 not the MKII version those are probably also Toshibas. Only the first series used RCA or Motorola Transistors.

 

[wg_ski]

Modern Motorola/ON devices, that is, anything later than 1990, are close enough matched to parallel properly if they are from the same lot (same date code). HFE isn't necessaily what needs to be matched - it's vbe that's critcal for safe paralleling. You should verify that they are within 3mV. Transistors off the same wafer will be - unless there is somethig seriously wrong. Things have gotten considerably better than when those old MJ15003's were first introduced. Toshibas were better than this a decade or more before Motorola caught up. Their real-wold SOA's were better too - another reason to use Toshiba.

Matching HFE is done if you want the absolute lowest distortion - trying to get thrid or fourth decimal place THD20k. That's needed between the NPN and PNP sides. And it will only be of help if the topology and layout support it - most times the output transitors are NOT the limiting factor.

 

[CIR Engineering]

Hello,
I would like to put something up here because some questions return several times about transistors of the 4004. What I know of this by now as red from an ebay page witch link perhaps you doe not know is as following:

http://www.ebay.com/gds/Classic-Aragon-Amps-A-primer-/10000000001149810/g.html

Here you can reed a statement from Mike Kusiak about used transistors of the 4004:
"The original metal case outputs [output transistors] of the 4004 were made by RCA or Motorola. Because of the great variability of the Vbe and Beta characteristics of these transistors, matching was essential. Without matching, one or more of the parallel connected output transistors would conduct all of the bias current, leaving the others off. Later, before the introduction of the MK II, Toshiba metal transistors began to be used. These were supplied by the manufacturer in sorted beta groups, which made matching much less critical... [the Toshiba metal case transistors] were also high quality, tightly matched, and designed specifically for audio amps. They were much better than the earlier RCA and Motorola outputs..."
The superior Toshiba output transistors can be identified by the name "MONDIAL" or "ARAGON" printed on the case of the transistor.


so if you find Metal cap transistors with printed Aragon or Mondial Label on an 4004 not the MKII version those are probably also Toshibas. Only the first series used RCA or Motorola Transistors.

My 4004 has the RCA transistors. I have Toshiba 2SD424/2SB554 in stock. Do you guys think it would be worth it for me to swap them out?

Can I upgrade my 4004 to MkII with the RCA's? Can I do the upgrade if I replace the RCA's with the Toshibas?

Edit: I also plan to upgrade the caps.

Thanks guys,
craigr

 

[Schurkey]

My 4004 has the RCA transistors. I have Toshiba 2SD424/2SB554 in stock. Do you guys think it would be worth it for me to swap them out?

Can I upgrade my 4004 to MkII with the RCA's? Can I do the upgrade if I replace the RCA's with the Toshibas?

Edit: I also plan to upgrade the caps.

Thanks guys,
craigr

There is more to the Mark II modification than just the transistors.

See my site for a downloadable instruction manual for the Mark II mods. (You will have to be creative in sourcing the parts.)

Aragon FanPage

http://www.hbassociates.us/004mkIIUpgrade.pdf