Motorola c-3000 Transitor

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Need 4 Motorola C-3000 transistors for repair of Carver M-400 amp. I realize this is a " house number from carver " . Does any one know where I can purchase these parts , or what ACTUAL motorola part number is. On base the following numbers are stamped. "H41" and " 457 " . Any help or direction would greatly be appreciated. Thank you. krazyz1
 
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Hi krazyz1,
Need 4 Motorola C-3000 transistors for repair of Carver M-400 amp.
Just use MJ15024 and MJ15025 to replace the NPN and PNP power transistors. Be very careful you don't break the transistor sockets. "Jiggle" as you tighten these, and before torque is applied. Make sure all the raised portions are through the holes. My pet peeve is getting one for service after the sockets are broken.

Use new mica insulators and fresh thermal compound, not for CPUs! Use less grease than was was originally applied. A thin coat on the insulators and transistors, a little thicker on the case work.

These amps are fun to service. What you need is a good memory and lots of patience. What you don't need is alcohol. :) A service manual wouldn't hurt either. Wish I had one so I could give you more exact help.

-Chris
 
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Hi krazyz1,
Thats the problem. Don't know if it is NPN OR PNP.
You are kidding me, right? :bigeyes:

If you don't know how to figure that out, there is no way you should be trying to repair any amplifier, never mind a Carver - and a Carver cube at that! These are not simple amplifiers.

No offense here, but if you were not kidding, STOP NOW!

I kid you not, if you are not very familiar with servicing amplifiers, do not proceed. If you will not pay to have it serviced properly, then give it to someone who will, rather than throw it in the garbage.

-Chris
 
kevvywevvywoo said:
Isn't the Carver number on there to indicate they've been graded at the factory?


They were aluminum-cased TO-3's. This suggests they were prior to the widespread availability of the MJ15024/5, which were always in the TO-204. The originals were probably graded 2N5630/6030, which most other amps from that vintage with series connected transistors used.
 
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Hi djk,
The original were Motorola MJ15015 and MJ15016.
That, I'll believe. The original low performance "economy transistors", to use Motorola's own words. These parts were all over the map.

If you really want the originals, I have them with late 70s date codes.
Sell them on Eekbay. "original Carver transistors with the real number on them. You could put a kit together and make a fortune the way people think. NOS transistors, and there is a market for them.

I would replace then all with MJ15024/25.
Without even thinking twice!

Plus, you should replace all the outputs anyway, not just the ones that have failed.
From an earlier post. Yes, but most of those transistors are commutating transistors. Was the driver transistor the same number on that one do you recall? It is on the newer amps.

Hi wg_ski,
From what I saw, these were not graded. There were no notations in any manual to suggest that grading was even remotely important. Good thing, considering these outputs.

The originals were probably graded 2N5630/6030, which most other amps from that vintage with series connected transistors used.
Nope. Those were better parts with closer tolerances. The MJ15015 and 15016s were used in products where fidelity was not the primary goal. The earlier Linear Power car amps used them also.

Hi kevvywevvywoo,
Isn't the Carver number on there to indicate they've been graded at the factory?
No. It is only a "house number" Pre-grading was often indicated with a different colour of paint dot on the upper casing of the transistor. Even when house numbers were used.

In the early days of servicing, even the part number of the transistor used was a "secret". This made life difficult for service people. Some specially selected parts had house numbers as well. Things like longer leads (Bryston) or higher break down voltages. the only way to be sure was to examine the schematic (that also was a secret and not often released).

-Chris
 
"Was the driver transistor the same number on that one do you recall? It is on the newer amps."

All the TO3 devices were either C3000 or C4000.

The driver for the top rail was the MJE3055/2955 pair.

Crown used the same MJ15015/16 for outputs in the PowerBase1, Microtech 600, etc. They tended to blow the driver transistors when running lower impedances (due to the low Beta at 10A).

On the aforementioned Crown amplifiers, you can easily double up on the outputs; on the Carver all you can do it put in the heaviest part you can find.
 
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Hi djk,
All the TO3 devices were either C3000 or C4000.
Yes, I know.

In many later Carver amps, they use the same part as the outputs as a driver, which is also mounted on the heat sink. I was hoping I didn't have to dig out a schematic to figure this out for this particular model.

They tended to blow the driver transistors when running lower impedances (due to the low Beta at 10A).
There are many brands that have had trouble with driver transistors packing it in. Carver was not normally one of these though. The typical failed Carver had a single output shorted. Some damaged back into the bias and driver sections, but they were a minority.

on the Carver all you can do it put in the heaviest part you can find.
Very true, but not normally required. There low impedance amp was a mono device using all the output locations for that one channel. Switching the rails gave Carver massive SOA compared to a "normal" design. Output failures were not widespread, especially when you look at how hard they were often run. The only unreliable position for a Carver designed amp was in the mids and up. These use would cause the commutator to "lock up" and the amp would go into thermal runaway if the levels were maintained into the second or third tier of voltage. Full range or bass amps were very reliable as long as the AC supply was good.

-Chris
 
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