Hartke HA4000 output blown

[pontiacpete]

Hi all, I'm about to rebuild the output of this amp. When I acquired this amp, I was told it wasn't working. I started it up on a light bulb and it was doing fine it dimmed as if there wasn't a short until I flipped off the current limit, then there was smoke and a little flame, ouch. These components are visibly burned; Q309 310 311 313 and R317. So, I am going to replace these and the ouput transistors. The previous tech used for Q314-7 2SC5200 for the D2155 and for Q318-321 2SA1943 for B1429 on the schematic.
My question, are these a good substitute for the originals?
And, what are good subs for the other transistors that are burnt?
Are the originals obsolete or are they specifically made for hartke?

[Jazz P Bass]

The 2SC5200/ 2SA1943 transistors are valid replacements.
They have the very same current (15A) rating & the same power (150W) rating.
The voltage rating is higher at 230V (180V).

[pontiacpete]

Thanks,
but I'm still not getting something here.. where do I find info/datasheets of the original transistors in this amp?
Also, for Q309 thru 313?

[Jazz P Bass]

Those transistors were made by Toshiba.
2SD2155 & 2SB1429.
Key word: 'were'.
You can find datasheets on the net.
I would stick with the newer number.
Higher voltage rating & the same current/ wattage.
It's a win- win.
Also, you will have better luck getting a more or less matched set of transistors (if they are from the same batch) when you purchase them from a big supplier (Mouser, Digikey, Newark)
The 'other' transistors are valid parts.
Simply put a '2S' in front of the number indicated on the schematic.

[pontiacpete]

Thanks so much JP.
Right now I'm trying to find Q312-3 and at mouser and digi I type in both with 2SA1266 and 2SC3198 and get nothing. Are these discontinued?

[Jazz P Bass]

2SA1266: MCM Electronics (Find 2SA1266 Stock and Compare Prices Across the Most Reputable Distributors in the Industry.)
2SC3198: MCM (Find 2SC3198 Stock and Compare Prices Across the Most Reputable Distributors in the Industry.)

[Enzo]

A quick way to find data sheets is to just google the part number.

2SC3198 and the other one are not critical parts. If you can;t find them, look at what someone else uses for the same purpose. For example, PV uses the MPS6530 or 6531 for the NPN, and the MPS6533/34 for the PNP. Crate used a 2N5088 and a 2N5087. Here is an Ampoeg with MPSA06 and MPSA56. SO really, a ton of basic signal transistors can do that job.


Now here is one for you. You can leave those two transistors out while you repair everything else, they are limiters and not really part of the amplification process.

Do yourself a favor and check some resistors. I don't care if they LOOK good, measure them. Each output transistor has three resistors associated with it. A large 0.47 ohm 5 watt power resistor, a little 4.7 ohm resistor to its base, and the little 220 ohm resistors over to the limiter from each emitter. Especially since your limiters burnt, look for open resistors.

If Q310 and 311 were damaged, then for sure check the two parallel resistors between them, R324/325.

The top and bottom line on the power amp schematic is the main power supply, now look just left of Q310/311 on those lines. See the 4.7 ohm resistors? Those feed the earlier parts of the power amp. Make sure neither is open.

Q309 is burnt? Then for sure check the resistors around it R316, 317 AND the bias adjust trimmer pot.

Y'know what? I see about a half dozen little diodes in the power amp. Set your meter to diode test, and just check them all in circuit. Looking for shorts and opens.

[Enzo]

A quick way to find data sheets is to just google the part number.

2SC3198 and the other one are not critical parts. If you can;t find them, look at what someone else uses for the same purpose. For example, PV uses the MPS6530 or 6531 for the NPN, and the MPS6533/34 for the PNP. Crate used a 2N5088 and a 2N5087. Here is an Ampoeg with MPSA06 and MPSA56. SO really, a ton of basic signal transistors can do that job.


Now here is one for you. You can leave those two transistors out while you repair everything else, they are limiters and not really part of the amplification process.

Do yourself a favor and check some resistors. I don't care if they LOOK good, measure them. Each output transistor has three resistors associated with it. A large 0.47 ohm 5 watt power resistor, a little 4.7 ohm resistor to its base, and the little 220 ohm resistors over to the limiter from each emitter. Especially since your limiters burnt, look for open resistors.

If Q310 and 311 were damaged, then for sure check the two parallel resistors between them, R324/325.

The top and bottom line on the power amp schematic is the main power supply, now look just left of Q310/311 on those lines. See the 4.7 ohm resistors? Those feed the earlier parts of the power amp. Make sure neither is open.

Q309 is burnt? Then for sure check the resistors around it R316, 317 AND the bias adjust trimmer pot.

Y'know what? I see about a half dozen little diodes in the power amp. Set your meter to diode test, and just check them all in circuit. Looking for shorts and opens.

[pontiacpete]

Thanks Enzo and JP
Got my order placed and I will be back with the results

Thanks for this;

2SC3198 and the other one are not critical parts. If you can;t find them, look at what someone else uses for the same purpose. For example, PV uses the MPS6530 or 6531 for the NPN, and the MPS6533/34 for the PNP. Crate used a 2N5088 and a 2N5087. Here is an Ampoeg with MPSA06 and MPSA56. SO really, a ton of basic signal transistors can do that job.

[pontiacpete]

It's been a while, but I'm finally back to this repair.
I replaced many bad components so far.
R328,331,334,337,340,344,347,350 were opened
R317 was burned open
R324 and 325 were the wrong resistors put in the correct value
Q301 to 321 have been changed
Now when powering up with the light limiter the amp stays in 'protect' mode. The light is not completely bright but not dimmed and pulses slightly
There is not DC on the output.
Does anyone have any ideas? Thanks

[Jazz P Bass]

If you are relatively sure that you caught it all, ditch the limiter.
Place a low value fuse on the line in, just in case.
I generally look at the output stage base voltages & the power rails when powering up a repair. (yes I have four meters)

[pontiacpete]

A 4A fuse didn't make it.

[Jazz P Bass]

Then I would suspect that there is still a shorted condition somewhere.
As the drained caps 'may' want 4 amps at startup (briefly), the output section certainly does not.
Less than an amp or something is still wrong.

[Enzo]

If the amp is in protct mode, the speaker relay will not turn on, so you won't have DC on the speaker terminals, but that doesn't mean the amplifier is not making DC on its output bus before the relay.

R324,325 are there to limit idle current, and if they went to a different value, I would have left them as they were.

If R317 is burnt open, then VR302, R316 and the posistor are certainly suspect, they set your bias along with that transistor.

[pontiacpete]

I'm not sure how to test the posistor, but R316 measures 1.8K ohms.
Can I disconnect it?

The replaced the trim pot, It was measuring 1.5k. I put a 500 ohm one in.

Still haven't found the short.

Is it possible that the relay isn't working?