I’ve been waiting on 430 or 730 twin but this came up in the meantime and I really fallen in love with the aesthetics of the unit. I don’t need super big power. I listen at very moderate levels and looks are important to me. Since I was cleaning things up after I purchased, I figured I’d reset idle current and any other service related items I could do. The service manual that I found had very bad instructions on how to do any of that work and some of it required function generator. Can someone guide me to an easier more simplistic way to adjust idle current and any other service related work that could be done without an oscilloscope and function generator?
HK three thirty nocturne
- Thread starter Caseymou
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Yeah she's a pretty little thing, that should keep you busy till the 430/730 twins show up. 
As far as adjustments go search the typical sites UTube, AK's search function etc. i would think if you had the specs on what numbers you need to achieve a decent quality DMM would suffice. But some manufacturers write their service manuals in such technical ways it can be intimidating. Good luck!
The tips at the bottom of our HK Nocturne Three Thirty point to an AK post that says “use the instructions from the Two Thirty instead. https://audiokarma.org/forums/threa...200-520-530-230-330-820.959956/#post-14789915
Here are this instructions:
Here are this instructions:
Here's a snip straight from the Three Thirty Service Manual explaining how to set the idle (bias) current and DC balance. Just follow everything underlined in red and ignore the rest.
If you don't have a scope or signal generator to set the DC balance, you'll only be able to set the bias by using a multimeter and adjusting VR502 and VR602 to get the desired 12 mA on each channel. What the manual doesn't say is to keep the volume knob turned down while doing this adjustment.
A word of caution. Since these variable resistors are getting close to sixty years old, they can be fragile and disintegrate while trying to adjust them which can cause a whole bunch of hurt to the receiver. If I don't have a set of new replacements installed or on hand, I have put a drop of DeOxit on them before trying to crack them loose with the power off and it has worked to help loosen and lubricate them. Also, make sure you are adjusting the correct one (there's two on each board) as I've caught myself happily adjusting VR's before with nothing changing on the meter or the screen and then realized I've been adjusting the wrong one. Then I have to start all over again.
I can work magic with a Sharpie!
They were marked so I wouldn't get any scope leads connected backwards to them. Visibility to the far side of the bench can be challenging at times.
i can't believe that no one has come up with the measurements needed to adjust this unit with only a voltmeter.
someone that has a scope and this unit should adjust the idle current according to the manual then turn down the volume and measure dc voltage across one or both emitter resistors and supply the voltage readout.
as far as dc balance: what about the way that is suggested on other units for people that have no scope?
i.e.: measure the power rail. then measure between ground and the input of the output capacitor and adjust for 1/2 the rail voltage.
@Mumbles this would work to "rough in" the dc balance right?
personally, i wouldn't go twiddling trimmers just to twiddle trimmers and that sounds like all the op wants to do.
someone that has a scope and this unit should adjust the idle current according to the manual then turn down the volume and measure dc voltage across one or both emitter resistors and supply the voltage readout.
as far as dc balance: what about the way that is suggested on other units for people that have no scope?
i.e.: measure the power rail. then measure between ground and the input of the output capacitor and adjust for 1/2 the rail voltage.
@Mumbles this would work to "rough in" the dc balance right?
personally, i wouldn't go twiddling trimmers just to twiddle trimmers and that sounds like all the op wants to do.
I’m pretty sure I know the answer to my question but manual doesn’t explicitly say where ma measurement should be taken. I believe it’s across the 8 ohm dummy load.
Yes, I'm pretty sure that is correct although it's been a while since I worked on a 330. I do remember hooking up across an emitter resistor on some model HK but not sure if it was a 330.
I usually take photos while working on these but will have to search thru them to see if there are any pertaining to this model and that might take a while as I have over 7K photos in my library.
OK, after studying the Two Thirty service manual more closely, I think we're onto something for setting the bias.
On the schematic, a hand written spec has been added and it shows a reading of 7.5 mV across R707 and R709. These are the white cement emitter resistors mentioned earlier and adjusted by VR502 and VR602.
The Three Thirty service manual doesn't seem to show the mV spec anywhere except for that 12 mA called for in post #5 so I'd first try setting the idle at 7.5 mV and see what happens. As usual, the manuals can be rather vague.
EDIT: The 330A and 330B call for 10 mV and 8 mV respectively so you can probably crank it up a notch without hurting anything. You might want to compare some voltages on these models first though.
EDIT: If anyone has a HK 300 (no letter suffix) service manual, it might contain the idle mV spec which would probably apply closer to the Three Thirty's than either the A or B models do.
First snip is the Two Thirty schematic showing the 7.5 mV spec while the second snip is the Three Thirty schematic. They are very similar layouts so I think adjusting should be the same procedure.
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