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Old 17th April 2011, 02:33 AM   #1
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Default Were MJ15024-5 equivalent available in 1994?

Were the 2.25 A @ 90V SOA (safe operating area) transistors like MJ15024-25 and MJL21193-4 available in the spring of 1994?
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Last edited by indianajo; 17th April 2011 at 02:49 AM.
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Old 19th April 2011, 04:09 PM   #2
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No helpers yet. My datasheet from On Semi for MJ15025 is dated March, 2001. It is pretty obvious Motorola was still operating in Spring,1994 when this PV1.3K was built. My Motorola semi library is dated 1975, and I wasn't getting updates in 1994.
The semi cross reference from Peavey in-house part numbers that Karsilik posted from electronicsclub.cjb.net lists 74200 TO3 transistor Peavey number (parts show 70484200) crossing to MJ15025.
What does anybody think about mixing one On Semi (real) MJ21195 with four Peavey/Moto 70484200 that electronicsclub thinks are MJ15025? What is different about perforated emmiter technology?
In a push-pull output with .5 ohm emmiter resistors on each, what does anybody think about using the 4 ea MJ15025 + 1 ea MJ21195 PNP's against NJW21193's replacements for 80484200 NPN's which are allegedly MJ15024 according to electronics club? All datasheets are on datasheetcatalog.com and PV1.3k amp schematic is on eserviceinfo.com.
Has anybody crammed a TO3-P (package 247) on a heat sink with TO3's lined up diagonally with 1mm spacing case to case? I can drill new holes for the leads but do I have to saw the corner of the heat sink off?
I realize if I just spent $48 on 10 real MJ15024/5 I could avoid these questions, but involuntary retirement is like that. The NJW21193's were $1.80 from an authorized ON semi distributor, I just couldn't pass it up. The MJ21195 was $3.60 instead of $5 for the MJ15025. I'm going to cook them with the PV1.3k hooked to 10 ohm 800 watt resistors, to see what blows up.
Yes, I removed the shorted out DC-prevention triac.
What does anybody think about putting 20 amp AG3 fuses in series with the power feeds to the output PCB to prevent land burning the next time the triac goes off? The capacitance on the output PCB is a mere .94 uf per side (+ or -)
I thought about putting relays in place of the triac, to lift when the bidirectional switch detected more than 8 VDC, and latch up with a spare contact run from the +-16 VDC supply, but I'm not sure my $2 4PDT telephone relays will interrupt a current from 20000 uf @ 95 VDC through a shorted to3 transistor. The last blowup, one O.T. die blew through the top of one of the steel TO3 cases.
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Last edited by indianajo; 19th April 2011 at 04:16 PM.
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Old 19th April 2011, 04:27 PM   #3
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Quote:
Originally Posted by indianajo View Post
Were the MJ15024-25 available in the spring of 1994 ?
"No helpers yet" could be because the questions are odd.

Motorola manufactured the MJ15024-5 long before 1994.
For examples, peek at some ML schematics, e.g. the ML29 (late 1980s model).
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Old 19th April 2011, 05:45 PM   #4
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Quote:
Originally Posted by jacco vermeulen View Post
"No helpers yet" could be because the questions are odd.
Thanks Jacco. I never do anything the normal way.
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Old 30th April 2011, 04:13 PM   #5
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Okay, anybody searchs PV1.3K, here on some answers on TO3-P transistors. You can put TO3-P transistors on the Peavey diagonal TO3 heat sink. You have to cut the corners of the heat sinks off to keep them away from the leads on the emiter resistors. This isn't very hard on the NMJ21194 transistor because the heat sink is copper alloy. The TO3 mounting kit, the mica insulator doesn't fit a TO3-P. I've tried and tried to find wide insulating pads from Keystone,wider than TO220; if they make them the applicability is a secret. Here is the PN of the mica washer for the TO3-P- Newark PN SOP9590. It is an inhouse part number so no point giving the multicomp PN. Surprise!- there is something new in insulating washers, a rubber pad. Found them under the dual schottky diodes in PCAT power supplies, also fits the TO3-P. I was nervous about them, no berylium grease, but apparently Thermaloy sells them and they don't need grease. I can't find them at Newark and I have to pay $9 freight from mouser in TX instead of $6, so I ordered mica insulator kits from Newark. The PV1.3k TO3-P replacements have all salvage PCAT diode insulators. You can bend the leads down on base and emiter on TO3-P (On semi njw21194 anyway) to fit through the Peavey heatsink, but the collector lead doesn't reach. I put an insulating ring through the B,E,and the unused C hole, and cut the insulating washer off to clear. I put a 4-40x3/4" screw, or a salvage 3mm screw when those ran out, through the unused C hole. I then cut the insulation off a red #6 ring terminal (dorman brand from taiwan). I bent the C lead of the transistor slightly to the side, shoved it through the ring terminal, and captured it under the head of the 4-40 screw on top of an internal tooth washer. I then put an internal tooth washer under the PC board on the 4-40 screw, and captured it with a nut. The head of the transistor is held with a 4-40 screw with flat washer on the heat sink end, so no collector current flows that way. The collector lead is soldered to the ring terminal, but no solder at the bottom of the screw on the PCB.
I hope there is not too much electromotive force from galvanism between the stainless hardware, and the copper alloy ring terminal and collector lead. Unfortunately, some of the screw hardware were actually steel, not stainless steel.
This style heat sink is also used on my CS800s, diagonal TO3 mount, so this technique should work on that to if I ever blow any transistors i don't want to spend $4.50 each replacing.
The soldering iron is not heating enough and I can't hook up the final emiter resistor to test point wires for bias measurement, so the amp is waiting another rainy day for the cap-explosion test (turn it on). Ordered twice as many 4700@100 caps instead of the $18 each 10000@100 caps, expensive because they have to be 70 mm tall or less. Old ones are only 17 years old, but that is a bit long in the tooth. Every other electrolytic has been replaced.
Having just spent $75 on a battery charger transformer burnt up by a shorted diode (lightning) I'm nervious about this 30 lb transformer and the rectifiers and caps, with no fuse. The charging current at turn on would be rediculous, so I'm ginning up a slow start circuit with a salvage 2 hp 2 pole relay, and 3 each 2 ohm resistors at 25 W per side of the cap chain. That should hold the initial current down to 30 amps, and allow 30 amp slow blow fuses in series with the rectifiers. Having to put a 24 VAC transformer in to power the relay coil, nothing available except the op amp +-16VDC, which needs no relay pop on it.
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Last edited by indianajo; 30th April 2011 at 04:41 PM.
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