Altec 9440a Transistor subs

[rstsgsas]

Noob here,just got an Altec 9440a with a blown channel ,I can fix it but I need some transistor subs,2n6421 to66 ,2n3584 to66 and the tz255 which i have not a clue what it is.Its on the parts list altec pn 48-03-12235-02 Any help would be appreciated.

[zelgall]

Replace the 2N3584 with MJE15032GOS-ND MJE15032G TRANS PWR NPN 8A 250V TO220AB ON Semiconductor NPN 250V 8A TO-220AB

Replace the 2N6421 with MJE15033GOS-ND MJE15033G TRANS PWR PNP 8A 250V TO220AB ON Semiconductor PNP -250V -8A TO-220AB

These are the common replacements in a variety of amplifiers that use your transistors.

See this link: Datasheet catalog for integrated circuits, diodes, triacs, and other semiconductors, view to crosscheck and verify that the specs are equivalent.

[rstsgsas]

Does it matter that the originals are TO66 (mini TO3) and the MJE 'S are TO 220ab?Any ideas on the tz255 part. Thanks

[zelgall]

The specs are the same but the case size is different. If you search on the linked site, they have links to suppliers that have your transistors.

[bfish]

It might be too early to help with a 9440, but there's some Altec transistor sub info in this old tech letter;

http://alteclansingunofficial.nlenet...rs/TL_175A.pdf

The item I had the most trouble finding new subs for were the Moxies (the two little thermal devices you can see through the holes in the heat sinks). I think I could dig up that info if it's ever needed. I might've even posted it here somewhere.

[rstsgsas]

Thanks for the info,some useful subs there.I am trying to get my ducks in a row before I dig into this. q9 of the schematic is a bias transistor tz255 is the altec number its part of the adjustment circuit with a variable resistor.I cannot find a reference anywhere on the net to it.I am not sure what will be needed ,just trying to see what is available. I will post later what I find and hopefully those thermal devices you speak of are still good.Digging for diodes too. I will update as I go. Thanks

[Russ Farrell]

If the 9440 serial number is #1660 or lower, the dead channel may be caused by the transistors loosening up on the heat sink. There were no star washers used in mounting them. Altec repair replaced the transistors on the numerous early units sent in. That "fixed" the symptom because they were tightened to spec when replaced, but the problem came back. A local user had the problem when he returned home from picking up his repair. He brought it back right away, and Altec found the cause. The vibration of the ride home had loosened the transistor again. The transistors were still good. Hope this helps.

[bfish]

Good memory Russ!

(I have to rely on more tangible records. );

http://members.cox.net/notthatstupid...ce%2001-76.pdf

[rstsgsas]

Thanks Guys, It seems there is more to this than a blown channel,The guy I got it from said it had blown a fuse but I checked that 1st thing and it powers up but no relay click.A quick check of dc on the output shows less than .2 volts on each side,I tried disconnecting each driver board seperately still no click,its a 24v dc relay but the feed shows only 10v may be a bad capacitor or diode. Thats where Ill start anyway.Anyone have any insight for troubleshooting . Thanks

[bfish]

The protection circuit path traverses every board in there, so you'll not have any luck with any board out. IIRC, it's the protection circuit that provides the relay coil V. Simply been too long to offer much from memory, but I can dig out the schem for a refresh if need be. A couple of things come to mind offhand, the push-on connector on the driver boards can cause problems, a small transistor and diode on the upper half of the driver boards are repeat offenders, and the foil paths on the control board are prone to lifting as well as the board itself is easily cracked by unprepared disassembly ( hold the front securely, it's heavy, and if dropped jerking the wires it's a problem).

Tha's all I got from memory. Trace the relay coil circuit back all the way and you'll probably find it.