Hartke HA2000 Part ID

[ChancesR]

Greetings all
I have this HA2000 on the bench. Came in with the symptom that it would cut-out, then back on again. Found a bad cap (C135, 33microFarad, 50V).

I was able to locate the schematic for this - also the HA3500. Neither of these show this part! I've traced the circuit as best I can, C135 appears to be connected to R356 (also not on schematic), and ultimately IC104/VR17.

I *think* this could be part of a thermal protective circuit, but I am unable to find anything to point me in any direction. Emailing Hartke only provided me with a Customer Service number - hmm. I'm really at a loss here. Any help will be so appreciated!

Thanks so much -

[Enzo]

Looking at the print for the Model 2000, which may or may not be the same as the Model HA2000, I find a 33/50v C135 conneted through a couple parts to IC104 and to a pot, though the pot is VR103, not 17.

Thermal circuits would not be in the preamp. This is not thermal, it looks to be part of the compressor. Specifically, the inoput signal from the preamp input jack buffer branches off to IC104 which then rectifies the sample adn charges that cap. That is the average level. From there the other half of 104 sends this control level signal into the compressor IC103.

If the compressor switch is OFF, this part should have zero effect on the signal.

The 2000B and the 2000 are slightly different. C135 is in both, but the R356 is only in the B. it was added in. If you have the 2000 drawing, find SSM2013 IC103 in the middle of the preamp. Immediately to its right is IC104 and further right is C135 and R139 right after the diodes. From C135, move north and follow the wire over to the top of the pot - VR103 on mine.

In the 2000, that pot is 100k. In the 2000B, they added the 15k R356 in series between C135 and the top of the pot. The pot itself is then reduced to a 50k. The net effect of the change is that the full range of the pot will become more useful and will not go up as high.

The main board number in the 2000 is 4005109100. The main board in the 2000B is 400109110. Look on the board, I bet you have the 110 board.

On the Hartke boards, I always inspect the film caps surrounding the tube. They stick up on their legs and vibration can crack their wires. Tug on each one gently to see if any need repair. This can cause cutouts.

[ChancesR]

Enzo,
You were right - this is version B. I do have the 110 board here. I'll recheck my schematics in the morning for that lost cap. ha Since you have the correct schematic, the R356 on this board is unreadable. It begins 56...but it's gone after the first 2 bands.
Thank you so very much. I can sleep tonight now.
Regards,
ChancesR

[Enzo]

Forgot to mention THE most likely thing: plug a cord from send to return on the effects loop jacks. If that restores sound, replace or service thee return jack. Always check solder under the jacks and all controls across the front panel.

[ChancesR]

I usually make solder connections, cracks in the board or any physical change in parts my first thing to do. I will take another look however. Thanks for that.
I found that the schematic I had found (downloaded in pdf form) is for the HA2000 Main board 4005182900. And C135 just isn't on there. Another oddity - this board has VR17, for the compression. You mentioned that ver. B showed VR103. There must have been several modifications to this amp. At least I know the purpose of this part of the circuit. When received, the amp was mid-point on the Compression dial - so the guy was probably running into this trouble because of the cap. I'll order a handful - just to be sure.
I'm going to go check those jacks now -

[lowell]

hey guys,
i've got this amp on my bench now. the amp signal fades out after being on for 3 minutes and turns to hum. The hum is only there if the compression is engaged. I have poked around in there and nothing seems loose. Any ideas?

[Enzo]

You have the amp he was working on? Or you have another of the same model? Threads are cheap, start new ones for new problems.

Get the schematic from Samson, and start looking for an IC with its output pin sliding to DC.