MT200 replacements for MJ15003 and MJ15004

[Audio Johnny]

Hello everybody.

First of all, sorry for my bad english.

I have a question and hope somebody can help me.

I want to rebuild the power amplifier of my good old Dynacord PowerMate 600 powermixer in an 19" housing.
This amplifier uses 2 MJ15003 and 2 MJ15004 (TO-3) output devices for each channel.

Due to mounting problems i would use MT200 (i think TO-247/TO-264 does'nt provide enough disipation power?) transistors. Can anybody tells me which one is the best (or the closest)
replacement for the MJ15003 and MJ15004 transistors?

If neccesary, i can post the schematic of the PowerMate 600.
Thanks in advance!

[jaycee]

MT200 is pretty much a Sanken format. They seem to be the only ones still making such transistors.

The problem is, all such transistors are going to have pretty high fT which will not be stable in an amp designed for MJ15003/4. Also, they won't be as good as TO-3 for dissipating heat.

If a 19" amp is what you want, and you are prepared to build, maybe you would be better to build something more recent, perhaps recycling some parts (transformer for example) from the Dynacord?

[AndrewT]

The 250W 20A To3 200degC BJTs (MJ15003/4) are very robust.
I don't think any other BJT can beat their spec.

Plastic packaged devices cannot compete.

[wg_ski]

Originally posted by AndrewT
The 250W 20A To3 200degC BJTs (MJ15003/4) are very robust.
I don't think any other BJT can beat their spec.

Plastic packaged devices cannot compete.

So use three instead of two. It sounds like you're changing the heat sinking arrangement anyway if you're contemplating changing T0-3 to MT200. If you use three T0-264's, you can pretty much pick your poison.

[Audio Johnny]

Everybody thanks for his/her answer!

I appriciate this. 6 Transistors in stead of 4 is a very good idea, but are the drivers (MJ15030 and 31) "strong" enough to "feed" an extra transistor? Can anybody tells me which one i can use the best? MJL transistors or something like that?

[AndrewT]

if you go for 200W plastic devices then I'd suggest you double the number of devices in the output stage.

Blame it on temperature de-rated SOAR.

[wg_ski]

MJL21193/4 will have characteristics and beavior more similar to the original MJ's than anything else you can get in a plastic package. And three will cost less than two Sanken MT200's.

[Audio Johnny]

That is great news because these one's are not so hard to get!

Maybe for future plans: do you know a good plastic case replacement for an MJ15022 and MJ15023 transistor? These are used in an PowerMate 1000.

Maybe the MJL21195 and MJL21196?

[wg_ski]

As for the drivers, the load will actually be easier on them with three MJLs. Beta droop in the outputs will be less. At 20A each, the beta of the MJ's will be down to 5 or 10. At 13A in each MLJ, it's still up above 12. Result - less current required from the drivers.

[wg_ski]

Originally posted by Audio Johnny
Maybe for future plans: do you know a good plastic case replacement for an MJ15022 and MJ15023 transistor? These are used in an PowerMate 1000.

Same thing applies. Bump up the size of the output stage by 50% going from TO-3 to TO-264. The 15022 is a higher voltage part than the 15003, but thermally similar.