Hartke 5000 Mystery

[gbono]

I picked up this amp off of Craig's List and the only info from the owner was that the amp would power up but no signal at output. Took the cover off the amp and found that the voltage regulator IC401 was hanging off the board probably damaged when the amp was dropped (one of the rack ears were bent). New regulator in place and the amp powers up but I only get a good clean/strong signal out of the send jack. If I inject a signal into the return jack or apply it to the front panel input jacks I get a very small output level at all 4 speaker output jacks on the back panel. I have the amp in Non-biamp mode (Mono).

I started to chase a signal from the return jack and found some very weird layout issues. The amp is a 5000HA with the following main board marked as: Model 3500B/5000/7000B 4005198010A. Looking at the signal coming off the EFX jack board I get a nice clean signal at the RE terminal of AN401 through the cable but when I look at the terminals of AN401 on the main board they are marked SE/RE/G but do not connect to the same components shown in the attached schematic. For example terminal RE on AN401 main board connects to R202 to C201 to pin 6 of IC107-B. "G" terminal connects to pin 3 and 5 on the same opamp. The SE terminal does connect to pin 1 of IC107 so that is why the send circuit is working.

With .5 to 1 VRMS at the return jack the output pin 7 of IC107 is not anywhere near the level of what is input at the return jack and if I chase the signal down to pin 1 of IC202 there is no way I'm any where near 12dB of gain.

Does anyone have the schematic for the above main board - the ones I find on the net don't match the layout I have? What am I missing?

[phatt]

I'm guessing IC107B is now wired as a follower (Pin 5 to Grnd)
The delete boxes suggest there has been a redesign. IC 107 B might be stuffed.

If Pin 3 and 5 are common then they are inverting stages.

Maybe you will have just redraw what is actually on the PCB then the circuit might make more sense.
Phil.

[gbono]

Found the correct schematic for this version of the amp. The preamp send gives a good clean signal and I can get 5VRMS into the amplifiers but that will only give a volt or so at both power amplifier(s) output. The power amp bias and supply voltages are correct so I cannot find a fault condition that exists for BOTH separate power amps.

Seems like I'm missing something obvious here. If the fault is not in the power amp circuit(s) it's in the protection components or ? I'm also assuming that you can run this without a load and still get an output?

[Enzo]

What if both amps have the same problem?  Pick one and fix whatever is wrong there.  That may fix the second in the process or at least tell you what it might need.

Note the heavey groun line in the PA, with the 10 ohm resistor breaking it in two?  Aer those resistors open?

[J M Fahey]

Found the correct schematic for this version of the amp.

Good, now POST it here

[gbono]

Here is the schematic that "looks" like what I have - note that it is almost unreadable. I received this from Hartke and they apologized for the unreadability but they lost many hi-res files on a server change. This schematic does have the correct send/receive circuits for my amp but there are other issues....

My PA boards have connector CN501 which matches the schematic previously attched (5000/7000). There is no R351 loaded on my PA boards just a jumper. The heavy ground bus doesn't appear to be correct for my PA boards and when I look for continuity between pins 1/2 (ground) on CN501 and R351 there isn't any. More mystery.  xP

It looks like the power transistors are glued down to the heatsink so removing the PA board to inspect the bottom of the PCB will be PITA.

[Enzo]

No one glues transistors, they are just large flat surfaces that stick.

[teemuk]

Agreed. It's most likely not glue but thermal paste. Yes, sometimes it hardens with age and sort of sticks like glue, sort of, but all in all you should be able to pull the transistors off the heatsink by carefully applying some pressure to them. ...Unless some idiot really glued them, but I'm quite sure it didn't leave the factory that way.

[gbono]

Errrr these are fully isolated (think TO-247) packages with some sort of pad under the part. Tried to pry them up but they won't budge - I believe the pad is an adhesive sil-pad

I also found that the output boards have type # 400597001 (see attached). Shows a connection between R351 and ground bus but again what I have isn't matching.

Any idea how to test the relay/protection IC circuits?

EDIT...with some heat and pliers I have all the power transistors freed up and can get to the bottom of the board. Checked all the capacitors around the protection IC and they are good. Will recheck the bias on the power transistors again and work backwards to the diff pair. After that I'm stumped

[Enzo]

Get a small screwdriver blade behind the legs of a transistor against the heat sink, twist it to wedge the transistor away from the heat sink.  They can stick with considerable force.

What does "isn't matching" mean?  You have a wire in place of the 10 ohm resistor,  OK that doesn;t change anything.  You have no continuity between that wire and AN101 pins?  Continuity from the wire to pins 1,2 of the main 6-pin connector?

Follow the trace from the wire (R351) back to the input co0nnector.  Any damage?   Try checking continuity of smaller parts of it.

Relay is easy, either it closes or not.  First find R334, 10 ohm 3w, in the output bus.  Measure its resistance.  It SHOULD measure zero ohms.  If it measures 10 ohms, your coil is open, probably broken free at one end.  Now the relay,  With the amp running and presumably ready to make sound measure resistance from that resistor to the output hot post.  You should show zero or very low resistance, that would be the relay contacts.  If it measures open, the relay is not closed.

Another way: scope the output at the speaker jack.  Now scope the output at R334, or at TP301, 302, any of those wil be the same.  Are they the same?  A closed relay connects those together.  If they differ, the relay is suspect.

[gbono]

R351 does not connect to pins 1/2 on CN501 or any pins AN101. The jumper at R351 is connected to the base of Q313 and the emitter of Q309. The other side of the jumper goes to R321 which is connected to the base of Q310 and emitter of Q314.

R344 measures at almost zero ohms. i'll scope out the test pointswhen I get the amp put back together. I assume you mean TP01 and 02?

[Enzo]

Do CN101 and AN501 ground connections have continuity to each other?

Dp emitters of Q309,310 have 150 ohms between them?

I have only your schematic to look at, test points there are TP301,302.  If they are labelled different on your board so be it, in any case I was just using them as convenient spots to see the output waveform on the inboard side of the relay contacts.  They are connected to two of the ballast resistors for output transistors.

[gbono]

No connection between pins 1 & 2(ground) on AN501 and any pin on CN101 on the PA board.

260 ohms between emitters of 309/310.

edit.........

If I scope the signal at R344 I get a nice large clean signal but at the hot terminal on the output jack it's clamped to less than a volt. The relay is the issue.

[Enzo]

OK, the relay is open, now check teh coil, is it being enegized or not?

[gbono]

The positive rail voltage shows up on the cathode of D310 so the coil is not energized. I checked the path between the B+ rail through R346, D310 to pin 6 of IC310 and there are no open components/traces.

I assume the coil needs to be energized to switch the relay terminal 2 to terminal 3 - closed path? If that's the case then IC310 is suspect - what are the +-VCC pins?