[theoneandevil]

Hallo!

Gibt es eine Möglichkeit beim Triamp (1. Serie) den Ruhestrom ohne Messadapter zu bestimmen?

Vor kurzem habe ich die Endröhren gewechselt und bin mit dem Ergebnis eigentlich ganz zufrieden - leider ist mir aus dem Schaltplan keine Möglichkeit ersichtlich, wie der Ruhestrom nachzumessen wäre. Soweit ich den Schaltplan verstande habe, gibt es keinen Kathodenwiderstand um den Strom indirekt über die Spannung zu bestimmen?

Danke schonmal für die Hilfe!

[zoranrataj2000]

1.
Zero Signal Current/Bias
You must remove the chassis to set the zero signal current or bias!
It is crucial that the zero signal current of the TriAmp power amp is set no higher than 60mA, otherwise the life span of the power tubes will be reduced considerably. Ensure all bias measurements and adjustments are performed by qualified technicians only. To remove the chassis from the amp head housing, proceed as follows:
- Unplug the TriAmp mains cable and detach all speaker cables, reverb cable, etc.
- Remove the rear panel of the amp so you have direct access to the tubes.
- Unfasten the chassis retention screws located at the bottom of the chassis and carefully pull it to the rear to remove the chassis from the wood housing.

Set your multi-meter to the 10-ampere range to narrow down the measuring error tolerance as much as possible. Switch the TriAmp on. Set the Master to zero with no input signal. Attach the meter probes to output transformer Pin 5 and Pin 2 of the tube circuit board. Set the bias of the power tubes via the TR 2 trimmer.

If the control range of the trimmer is insufficient, replace the R128 resistor with a 3.3 K-ohm resistor. If this change does not increase the control range by a suitable margin, replace the R129 resistor with a 120 K-ohm resistor.
(see Diagram 8, TRIAMP Chassis)


2.
Zero Signal Current/Bias 2
For serial numbers 180 000 to 180 500, the bias may be set to approximately 75 mA. In a few cases, this may lead to a reduced life span of the power tubes.  If you find the bias is 75 mA, then proceed as described in first part.

H&K     

I own 25 H&K amps and cabinets.

[cca88]

1.
Zero Signal Current/Bias
You must remove the chassis to set the zero signal current or bias!
It is crucial that the zero signal current of the TriAmp power amp is set no higher than 60mA, otherwise the life span of the power tubes will be reduced considerably. Ensure all bias measurements and adjustments are performed by qualified technicians only. To remove the chassis from the amp head housing, proceed as follows:
- Unplug the TriAmp mains cable and detach all speaker cables, reverb cable, etc.
- Remove the rear panel of the amp so you have direct access to the tubes.
- Unfasten the chassis retention screws located at the bottom of the chassis and carefully pull it to the rear to remove the chassis from the wood housing.

Set your multi-meter to the 10-ampere range to narrow down the measuring error tolerance as much as possible. Switch the TriAmp on. Set the Master to zero with no input signal. Attach the meter probes to output transformer Pin 5 and Pin 2 of the tube circuit board. Set the bias of the power tubes via the TR 2 trimmer.

If the control range of the trimmer is insufficient, replace the R128 resistor with a 3.3 K-ohm resistor. If this change does not increase the control range by a suitable margin, replace the R129 resistor with a 120 K-ohm resistor.
(see Diagram 8, TRIAMP Chassis)


2.
Zero Signal Current/Bias 2
For serial numbers 180 000 to 180 500, the bias may be set to approximately 75 mA. In a few cases, this may lead to a reduced life span of the power tubes.  If you find the bias is 75 mA, then proceed as described in first part.

H&K     

I own 25 H&K amps and cabinets.

Hi Z,

what's the HV the triamps are running on? I can see no apparent reason, why a healthy EL34 or a 6L6 should suffer from a current of 30mA pr tube @ 450-470V B+?

@ Hallo:
Die Method funktioniert zwar, es gibt aber etwas zu  beachten: wenn Du mit dem  Multimeter auf Strommessung hantierst, hat es einen sehr geringen Widerstand.
Was heißt das? Nachdem Du direkt auf der Anodenspannung mißt, bedeutet jeder Kontakt mit MAsse einen mehr als saftigen Kurzschluß von ~470V auf Masse!!!!

Mein Tip (mach ich in dem Fall auch selber)
Klemmhaken verwenden; Amp ausschalten, klemmen, Finger raus - messen.


Grüße

Jochen

[zoranrataj2000]

Hi!
I paste from service manual for TRIAMP Mk1.Probably H&K know,why is this so important if they have in own service manual.I just wish to help with original settings.
I use bias adapter.And I ask again(H&K) for 30mA, beacuse 30mA is a little cold.I get confirm again, 30mA bias for 1 tube,60mA for 2 tube.!
I made for myself and for my friend 34mA for 1 tube.It sound much better and hot on2 and 3 channel.
They probably have hard working preamp and power amp should be clear as possible.
Zoran

[Dirk]

I use bias adapter.And I ask again(H&K) for 30mA, beacuse 30mA is a little cold.I get confirm again, 30mA bias for 1 tube,60mA for 2 tube.!

That's right, it is a little bit cold but also saver than 34 mA even if there is no big difference. H&K takes no risk.

Best regards, Dirk

[raven]

Hi Zoran,

I own Triamp combo (I think only 400 combos produced in 1995), really nice beast I must say  -  I got it second hand with original H&K 6L6WGC power tubes - I have to replace power tubes now, and set the bias - from your posts I can tell that you have experience with H&K Triamp so I hope you can help me with this:

1. Do I definitelly need a tube adapter to measure tube's cathode current or there is a terminal on the PBC (or some other points, like conectors between main board and fuse board for example) where I can (and it's safe to) do the measurement ?

2. I also want to change caps which is suggested for 15 years old amp, expecially becase this apmp was sitting unused with previous owner for almost  5 years) - I sent en amail to H&K asking for spare parts listed in Triamp's service manual but I recive no answer so far - what would you recomend : keep calling H&K for this or buy caps from other address (can you suggest where to buy via Internet because I can purchase those locally)?
There is a local H&K distributor but it will take a long time and almost double the price if I order H&K parts via the distributor (no local H&K service).

3. You said that you set 34mA bias for your (or friend's?) amp - can you feel the difference in the tone ? Which lamps you use and where did you purchase the lamps?

4. There is hum balance trimer (near to bias trimer) on the main board - do you have any experience with this ?

5. On my combo there's an external pot on the back down side of the chassis, do you know in any chace what is this pot used for (might be a mod)

Thanks in advance.