Hard to find transistor...

[pflodin]

Hello all.

I'm trying to repair an Hill audio DX1500 Power amplifier and I need to find replacements for the originally used H001A B1 NPN Power transistors. I suspect that these transistors are (H001A B1) are ifact some kind of standard bipolar transistor vitch has gone trough a screening / matching process, but I'm not shure.

Anyon that has any info on this ?

Regards

Peter Flodin

[pflodin]

OK, Ill try this istead, witch transistor could replace those on the drawing attached ? Rail voltage is +- 80V and rated power is 300w RMS @ 8ohm , 500w RMS @ 4ohm and 750w @ 2ohm.

There seems imposible to obtain the original transistor (H001A B1) and the manufacturer of the amplifier (Hill) doesn't exist anymore.

Could a MJ15003 do it or....

/Peter

[pflodin]

and the drawing....

[moamps]

MJ15022 is better choice for +/-80V rails.

Regards
Milan

[john curl]

First, let me ask a couple of questions: Is the transistor in a TO-3 package?
How long ago was the amp first made, 1 year, 10years, more than 10 years? How many parts are in parallel, if any, at the output?
You have MANY choices available, BUT we want to make the replacement device compatable with the original part.
For example, the MJ15003 is a SLOW part, but rugged (for 25 years ago). There are faster parts with the same ratings today, but they are usually in a different package. If the output devices are in parallel, you might have to replace the whole side of parallel devices.

[cunningham]

There has to be more in parallel if these specs are correct. Or there would be lots of

[pflodin]

OK, I'll take it from the top.

The amp is a professional power amplifier of the brand Renkus-Heinz but was manufactured by the brittish company Hill Audio Ltd sometime in the late 80s (or early 90s maybe). Each channel is built on eight NPN bipolar transistors (TO3 case), four and four devices in pararell with a with a 0,33 ohm resistor on the emitters.

The rail voltage is +-80V (transformer is 2x65V)

10 out of the 16 transistors seems to be broken (shorted C - E ), so the plan is to replace all the transistors with new ones. I allso found that one of the emitter resistors was broken (infinite resistance), but I don't know if that hapend when the amp broked down.
When this happend the amp was running in bridge mode with a load of 4ohm (two 18" subwoofers, 8ohm each).

It seems to be a litte odd to use only NPN devices, but in the manual the manufacturer says "Using a unique transformer coupled driver stage, the DX1500 features identical ultra-linear NPN output devices connected in a Super A sliding bias configuration exhibiting a much more linear response than conventional amplifiers using NPN and PNP devices." ?????

I have tried to post a clip from the schematics, but it seems to have been lost in transit....

/Peter

[cunningham]

Does anyone know what the maximum LINEAR current operation is of the MJ15003/MJ15004 pair???





Chris

[pflodin]

I dont understand this, I try to attach a file several times, but they never show in the message......

I'll try again..

/Peter

[djk]

The original part was probably a house numbered MJ15024, rated at 160W SOA at 80V. The new MJ21196 is 240W SOA at 80V and is the same cost.

http://www.onsemi.com/pub/Collateral/MJ21195-D.PDF

A schematic for the "Hill Heat Generator"

http://www.diyaudio.com/forums/attac...?postid=246697

The MJ15003 is only 120W SOA at 80V, but will not take more than ±70V unless hand selected.