where will teach me theory of old solid state output stages?

[thetragichero]

i'm sure i'm approaching this from the wrong angle but also confident the brain trust around here will nudge me in the right direction...

i've picked up another old organ to strip (1978 lowrey d-500/sct... original retail price about $6800 so like 30k in today's dollars... wow!) so with all the speakers and the leslie and miles and miles of wire (not to mention a bench and some other parts made of walnut to add to my 'will laminate and make guitar bodies out of someday' pile), i've got another rugged power transformer along with a ton of power transistors (looks like they contracted motorola to put their own part numbers on them, but after some googling the darlington power transistors appear to be comprised of mj901/mj1001 equivalent transistors)

so i know just enough about this stuff to get the soldering iron hot and do some real damage (or follow directions and troubleshoot/repair stuff like that kustom head), but i'd love to understand a little more than just painting by numbers/insert part number here. things such as:
looking at the datasheets for mj901/mj1001, Vcb is 80V max instead of 100V for a 2n3055. where can i use these found transistors (in say the old RCA power amp circuit that it seems kustom just completely lifted... roughly +/-40V supply rails) and where i cannot
when to choose complementary NPN/PNP pairs for power transistors (like this organ uses) and when to use darlington/sziklai pairs (as it appears this kustom power amp does)

i have this 2U rack enclosure i paid WAYYYY too much money for off mouser years ago that i'd like to build a stout solid state amp into (the sunn beta bass/beta lead is going for INSANE prices on the used market. i'd rather make one from odds and ends. it's the nutz way, after all!)

basically i would've loved to have become interested in this kinda stuff while i was racking up 40k-ish per year in student loans attending a tech institute as i could've learned more than just the right hand rule (throws up physics gang sign)
any links would be much appreciated

[sumgai]

trag,


Nearly 10 years ago(!!), JohnH posted a US Navy training course about electronics. Sadly, that original link went down, but the thread was updated by monkey hotel a few years later.

Now, with some of MH's links also dead, I checked the Wayback Machine, and wouldn't you know it, they've got the complete set of manuals for the entire course. Go here:

guitarnuts2.proboards.com/thread/4359/electronics-course-navy-updated?page=1

wherein I posted the direct link to the Wayback Machine's cache. So you don't have to drill down like I did.   And also so that others can find the latest link without having to visit this thread as well.

HTH



sumgai

[thetragichero]

i will load this on my phone for evening tv time (when i do my best reading lol)

i took another look at the sunn beta schematic and it uses 2N3055s on one half and a PNP compliment (in this case MJ0954) on the other half of the push/pull output stage so for that case in specific as long as the lower Vcb voltage handling is okay, i plugging and praying should suffice

but yes, this should definitely keep me busy

thank you! :-)

[sumgai]

trag,

The better choice for a PNP "match" to the 2N3055 is the 2N2955. The MFJ series of semiconductors are good replacements, but not exactly the same... they were intended for a wide variety of replacement chores, and like all such "do it all" components, they suffer in some respect when compared to the original.

In my time, I had several Sunn Betas pass over my workbench, and I've seen both the original output transistors and several kinds of replacements. More than anything else, this tells me that the Sunn designers "played a little too close to the fire", and over-stressed those output units. But Holey Moley, they were LOUD!

OTOH, humping those speaker cabinets in and out of venues took two men and a small boy, lemme tell you!   Come to that, I always figured that if I was gonna play Charles Atlas, I might as well bring the Big Boys to the party, and just fetch out some Ampeg cabinets. Either that, or up the beer rations for my roadies!

HTH




sumgai