Help with Hartke HA2000 Passive/Tube Volume input distortion...

[Edzone]

Hi dears new here, soliciting yours help & assistance on a Hartke HA2000 bass amp. I'm servicing.

1)I has replaced the two broken input jacks (with same originals), the IC101 (with same NJM2068DD) and the Pwr Supply Regulators 7818/7918
which I substituted by the 7815/7915 because same numbers are Not found.
2)The amp is now working & sounding almost well BUT except by the PASSIVE Tube Volume input.
3)When a signal is in to the ACTIVE input it sounds good with Solid State & Tube Volume controls at all levels from low to high.
4)with PASSIVE in signal, only with the Solid State Volume sounds good at all levels, but with Tube Volume heards a distortion like cracking
from low to up.
5)I has checked and replaced the R101 (68Kohm), the 12AX7WA valve and another time the IC101 (NJM2068DD), but with no any good
results, keeps same failure.
Have anyone some suggestions, directions or knows for some modification or upgrade to fix on???, can be the 7818/7918 substitution by the
7815/7915 causing this distortion on the PASSIVE w/Tube Volume only???
Thanks and will waiting.

[soundguruman]

Well you did reduce the headroom by using 15 volt regulators instead of 18 volt. 7818 and 7918 are very common and easily available.
and you may have a bad solder connection or a bad plate resistor.
All you need is an O scope to track it down.
As far as the amp goes, I think you will experience power amp failure. There are some problems with the design, and a bunch of them have blown up.

[Gtr_tech]

As far as the amp goes, I think you will experience power amp failure. There are some problems with the design, and a bunch of them have blown up.

That mainly applies to the mosfet version which had a tendency to violently blow up. The std bipolar ones are pretty reliable.

[soundguruman]

I have two bipolar amps sitting in my shop. Both of them exploded.
In addition to this, customers reach the rapid conclusion that there is no service or parts support for these amplifiers, made in Vietnam.
From the standpoint of people who bought these things, you may have made a mistake.

[Edzone]

Hi everyone and thanks for your very amiable replies. Notice that the amp section module is completely good and original genuine, what only I does with was
to clean it and resolder many bad look contacts. The main problems was on the main board (#4005109110 which includes the SSM2018 IC and not the 2013 as
another pcb version) nothing difficult and serviced but except the distortion (cracking sound) failure presented now when to change the Tube gain (Volume)
potentiometer from -to+ and connected to the Passive input only. The very rare thing here is that the 2 input volume pots (Solid State & Tube) are common for
the 2 Passive and Active inputs and works and sounds great except for the Passive input/Tube volume. I has checked continuity on grounds, on many circuit
tracks, resitors & caps values but nothing. What only I think may be the replacement of the 79/7818's regulators by 79/7815's. Will try to find the 18's to
replace them again and will be informing. THANKS!!!

[Jazz P Bass]

Mouser Electronics has the regulators
LM7818/ positive 18 volts
Mouser Electronics - Electronic Component Distributor LM7815
LM7918/ negative 18 volts
Mouser Electronics - Electronic Component Distributor LM7915
I like to use Find Chips.com.(FindChips.com Online Electronic Component Distributor Inventory Search)
It queries the major distributors for availability.

[Edzone]

Thanks a million Jazz P Bass, yes i will be ordering them.

[g1]

Unless the HA2000 preamp is very different from the HA3500, the problem as you are describing it is not really possible. If the fault is in the passive input, then it must be there whether using the tube or SS volume control. If the fault is in the tube volume circuit, then it must be there whether using the passive or the active input. It may not be noticeable to your ears, but you would probably see it on the scope.
I believe you need to think about the problem differently, you are thinking about the fault in a way that is preventing proper troubleshooting.

[soundguruman]

Want Parts? Try Jameco. They ship postal service to save you money. 7818, 7918, no problem I think.

[Edzone]

Hi g-one, according yours comments notice please:

"the problem as you are describing it is not really possible"
R/. The problem described & presented are very very strange and really possible, I have it.

"If the fault is in the passive input, then it must be there whether using the tube or SS volume control. If the fault is in the tube volume circuit, then it must be there whether using the passive or the active input."
R/. I completely agree with you on this comment, and this way will be better to check and find the bad component to repair it .

"It may not be noticeable to your ears"
R/. But yes!, it's very noticeable.

The worst is that failure presents with Passive input & Tube vol control only, Passive & SS vol control works great. Very STRANGE Failure!!!
Tracing the signal, distortion starts at pin 1 of IC101 and pins 2-3 of 12AX7WA, again but only with Passive & Tube vol control combination.

Thanks.

[soundguruman]

I don't see anything the slightest bit "strange" about it. Op amps short circuit all the time, and frequently. Distortion at pin one= blown op amp. You will also notice that when the op amp blows, it gets hot when operating, usually.

[g1]

If you are using the same level of input signal for the different inputs, that could be why you don't notice it when using the active input. The active input is expecting a hotter signal level so I would expect less gain there. Maybe if you increase your signal level to the active input you will hear the problem?

[Edzone]

FIXED! Hartke HA2000 Passive/Tube Volume input distortion....

Hi everyone, well finally it are now fixed. Was nothing bad with the Passive/Tube circuit, but the input sensitivity signal I'm using
was to much higher (hotter)than this circuit required. Rest of the repair is OK (change of the two input jacks and from IC101 to 105).
Thanks for all your suggestions!!!

[soundguruman]

groovy.

[J M Fahey]

So g-one was right all time long.
And supplied *useful* info

Unless the HA2000 preamp is very different from the HA3500, the problem as you are describing it is not really possible. If the fault is in the passive input, then it must be there whether using the tube or SS volume control. If the fault is in the tube volume circuit, then it must be there whether using the passive or the active input. It may not be noticeable to your ears, but you would probably see it on the scope.
I believe you need to think about the problem differently, you are thinking about the fault in a way that is preventing proper troubleshooting.

and:

If you are using the same level of input signal for the different inputs, that could be why you don't notice it when using the active input. The active input is expecting a hotter signal level so I would expect less gain there. Maybe if you increase your signal level to the active input you will hear the problem?

And, by the way, this problem is completely unrelated to the amp being made in Vietnam or Korea.
In fact, afaik big Hartke heads were made in Korea; it's Ampeg which moved to Vietnam.
But soundguruman does not know that.
Even worse, thinks Korea, Vietnam and China are the same Country.
Oh well.