Hartke HA5500

[Smokerx]

Update:On the HA5500.. I replaced another old Transistor on the rails that cooked off and Q308 for the 2nd time. Its dim bulbing, now and the fans are running, but the safety relay wont pass the signal to the amp. I dont hear the usual relay clicking on and off from the power amp board. So I got it working enough to take measurements off. A thing I noticed is the HA5000's Volume and Preamp pots feel different. When you turn the knob theres a feeling of slight wiper resistance. When you turn these knobs on the HA5500 it feels like theres no resistance whatsoever. Too smooth and too fast.

Also the solder is so old and dodgy its hard to melt and seems to want to take its landing trace with it. Its like the landing trace is poorly adhered and the solder is mostly oxidized.

This all took me a minute because I left my only tube in the HA5000 (still working fine) and had to get a new tube to continue on the HA5500.

TLDR: HA5500 has gone from "Blows fuses" issue to "relay wont pass signal"

[g1]

IC301 is the protect IC that turns the relay on and off. If there is DC at the output (R334), the relay will not turn on.

[Smokerx]

False positive: Relay wont turn on because Q312 was blown open. No Continuity. Usually the transistors have blown closed. Once Q312 is replaced its right back to square 1 with no fans running and a bright glowing dim bulb. I guess thats good, since the issue obviously lives down stream from Q312.

Q308 was replaced. It then passed signal to Q312. which cracked open...(Q312 was also replaced on attempt 2 or 3 tho. So Im cooking fresh, possibly fake parts off) I did measure VDC on the entire "low amp side" btw. (Q319 rail)

Low amp High Amp markings on the amp board are weird to me. Since I looked up Class AB amp and it looks like its handing signal back and forth across those rails in a wave form. So half the signal reached Q319 I guess.

Seriously wouldnt be surprised at this point if all my parts are fugazi and the rails backs got blown out again. Will take it apart and start testing transistors again. never give up. never surrender.

[Smokerx]

HA5000 probably just blew again. I was playing at medium volume through the solid state. Heard something cut in and then demon noises sent to speakers. Clicked it off. Turned the volume to 0 Turned it back on with the dim bulb installed. Dim bulb glowed dim, Relays passed the signal but demon noises through the speakers with volume set to 0. It somehow bypassed the volume knob and sent demon noises.

No clue how to proceed. Dont have a tube tester. But I just switched tubes to a GE vintage tube to get the Groovy tube out of the HA5000 so I can use it to continue attempts at repair on the HA5500. So I'll switch the tubes again and see if GE tube is the culprit. No clue how the Tube preamp knob all the way down and the volume knob all the way down would send signal through a shorted tube tho.

But this is the only thing that changed and the amp never did this before, besides when I got it and swapped to a known good groovy tube.

UPDATE:

The groovy tube fixed it. Its hard to say for sure as the problem just manifested once the amp heated up and then I let it cool down so I need to give it some time b4 I announce this is definitive.

Oh yeah, back to square 1 of having 1 definitive working tube as the GE vintage tube now goes in the box as a suspect tube next to the demon tube...Maybe theres something to the warning hand written: "DO NOT UPGRADE TO A 12AX7A TUBE!!! ITS OUTPUT IS TOO HIGH AND WILL "COOK" CIRCUITRY"

...Well Ron W. all the literature on this I can find is the A is a manufacturers designation. But comparing the getters between the known demon tube with no markings, the GE 12AX7 and the groovy tube 12AX7 the internal design looks different.

ALSO I didnt pay $1 million for a POS vintage GE 12AX7. It was the cheapest tube I could find. If I could have found a New Chinese tube for cheaper I would have bought that. But figured swap tubes for the tube I know works and didnt have a problem with the GE vintage until I just did. I also almost always play only Solid state with the tube knob set to 0 as the noise difference seems like a gimmick and I suspect the hybrid design is what cooks these amps.

Here's a pic that matches the internal design of the manufacturer unknown demon tube and the GE tube I just yanked



Heres a pic of the internal tube design I havent had an issue with. The specific designation is a Groovy Tube 12AX7R on mine.



Thread I pulled this image from
https://www.thegearpage.net/board/in...beled.2475209/

Not interested in Tonality Im specifically interested in discovering why these amps seem to self destruct.

[Smokerx]

On the HA5500, I took the good groovy tube and tested it with that. Since Im getting dim bulb but no relay click. took the operational amp board back out, looked at it for blown apart transistors again and cant find a blown transistor. So decided to look at voltage across the rails and heres the results...


Heres, what this other guy is seeing



So Yeah thats not good. I pulled the tube and tested with the tube out and got even more 125 volts with a dim bulb.

Took the groovy tube and put it back into the HA5000 and gave it about a 20 minute session to test, The tube is still working and doesnt appear to have been damage while plugged into the HA5500. No sudden or intermittent demon noises for the full 20 minutes.

[x-pro]

At 112V, with plus on bases Q313,315,315,317,319 they are either burned out or resistors R324, 326, 328, 330 are burned out. Check R321, Q309, Q310, C307(on 200V).
What is the voltage on b-e Q309 ?

[x-pro]

When measuring this voltage, where is the plus of the voltmeter?

[Smokerx]

Previously I stated the HA5000 tube shorting possibly produces the demon noise. Just gave it some more time playing and it did it again with the groovy tube. So I can rule out the tube as the culprit. Heard the fan click off and a static switch noise. then demon noises slowly raised volume. Its hard to describe the exact noise coming out of the speaker. Its a vvrrrrRRRRRRRRR that slowly climbs in volume. So far Ive been able to flip the off switch before it damages speakers or components. It cools off and I can run it again and plays normal.

I heard these things run hot. so its now possible its overheating and I need to adjust it to run colder? offset or bias?

Thanks X-pro. I will test these components you posted on the HA5500. First I will go over all components while the amp is off, because I dont like testing with my meter while the amp is running voltages. Just gave it a real quick test while the amp was running. Saw over 100 volts and said yup. its not a bad protection relay.

My cabinet is rated for 500w RMS and the HA5000 demon noises should be maxxing at 340 watts at 8 ohms. But it could be going over that since this is probably what is blowing up the Operational amp boards.


UPDATE: that was helpful x-pro. all my resistors R324,R326, R328,R328,R330, AND R325,R327, R329, R331 are in various states of blown. Some blown open some blown closed.

[Smokerx]

Oh the hunt for cement through hole resistors. Heres the digikey data sheet, as Im aliexpress shy now..Wow..just wow...


OK I just ordered some on ebay because I trusted that mans dirty hands. See you guys in a month..

Ok I figured out how to test the tubes with a multimeter. Continuity across pin 9 to 4 and 5 on all 3 tubes. no continuity on the rest of the pins. so no tube in the 3 tubes is shorted.

I back probed the molex to the speaker outputs and adjusted SVR301 on the right side amp driver down to 0. Im getting .008 volts on the left side and will attempt to adjust it down later, because Ill have to take the Opamp board out to get access to SVR301 on that side.

I messed up and just assumed when the amp cools off it wont send the demon noises. So flicked it on and immediately no fan and A giant horn noise blasting out of my cabinet so Im hoping my whole speakers are not blown. If the fan stops then the power that should be spinning it are going to the speakers to make demon noises. The Safety relays are not protecting me here at least in the mono setting on the HA5000....

I assume I can use back probing the molex to protect against demon noises as I should be reading major voltage. If no voltage the amp is operating appropriately is my guess. But I havent caught the major voltage and no fan running on my meter yet.

Ok If I had to guess by ear the hum is 120HZ. so Its possible this is just amp hum? and a 500watt RMS 4x10 is just this loud with filter cap hum? Is filter cap hum volume knob dependent? I usually play with the volume setting barely on maybe 5% on the solid state preamp pot and 5% on the volume pot. What worries me about this diagnosis is the case fan not spinning. I know I get dim bulb with that noise blasting out the speakers tho. I might just replace the filter caps to rule them out here.

[Jazz P Bass]

Late to the party here.
I seem to recall having test issues with one of these units.
There are ground points on the PCB that get attached when the board is properly installed in the chassis.
If you are working on the board out of the chassis, these points must be jumpered.
I don't have the information of what points they are.
You will have to do a visual search.

[Smokerx]

From what I can tell with the multi meter theres a few ground plates/washer things on the preamp board screws. The amp driver board I couldnt establish a ground with from the mounting screw to the heatsink and heat sink to case. so I think the ground here is established from the main power molex back to the preamp board to ground. If I remember right I scratched a bare metal spot on the driver amps heatsink then measured back to a ground to verify it didnt establish a ground to the case from Heatsink to case. But will verify this.

here its impossible to measure on or tune pots on the driver amp board without it dismounted and the output jack board dismounted. I built some alligator clip jumper wires as accessories to my meter I can use to jump to ground and will keep this in mind. Along with some needle probe tip adapters for back probing. I wish some1 told me those 2 upgrades are mandatory the day you buy your multi meter or they came with the meter. I think it took me 5 years to order needle probe adapters and a pack of electronic alligator clips to build some jumpers. Worse is the needle probes dont even fit my probe tips so I had to shim them with aluminum foil.

[Smokerx]

Im still googling how many decibels is 370 watts of amp through a 4x10 cab...No luck..If thats back ground hum from bad filter caps its loud. Like everytime I hear it Im afraid its going to explode my expensive cabinet. What I did find is filter caps can fail and draw power. Which might indicate why the fan suddenly cuts out, as plugging in either driver amp main molex has no effect on the case fan. I also found a guy saying "this is the worst bad cap hum I have ever heard" on an amp. Possibly indicating theres various decibel levels to cap failure? The noise it was making was almost spot on. Only difference is mine is ear bleedingly loud and Ive permanently damaged my hearing.

https://www.youtube.com/watch?v=vR7v0gs_asc

[nosaj]

Yep broken ground somewhere. These can be hard to find sometimes.
nosaj

[Smokerx]

sanwha caps out. Nishikons in. Waiting for the electrics to dissipate before taking the left channel loose to tune its hidden offset pot. I dont think its a broken ground. Why would it suddenly shoot 120 hz after 5 minutes of heavy playing just sitting there? I had the nishikons on hand just didnt bother replacing the filter caps if the amp worked. Which it did until intermittent deafening 120Hz. Im sold on bad filter caps. because THEN its fixed.

Ok I just tested again the main molex unplugged measuring continuity to the securing bolt for heat sink to case and the corner screws for the pcb passes continuity. So thats a ground and Ill jumper wire while tuning the hidden offset SVR301 pot.

Got the left channel down to .8 millivolts. i still need to tune that channel to 0 but way closer. Powered it on and no fog horns, yet. Powered it up and the new caps sound alot punchier. Not conclusively the caps tho. Since I have to give it some time to play fog horn noises intermittently.

.03 volts is the closest I can get the offset.