[AKSA]

Hi Nick,

You are pretty close now......

LEFT CHANNEL

Across R12 1.26v
o/p to gnd 0.8v
across R8 0.62v (sure i got 2,5v here at one point)
across R4 1.54v
gnd and R12 14.42v
gnd and R8 -14.49v

Across R31 33.5v
gnd to R31 139.4v
*** gnd to R23 49.5v(dc) 109.3v(ac)
*** across R26b-R27b 2.4v

Top section, SS gainblock, is fine.

Second section is pretty good too until we get to R23 and R26b/R27b where you are probably measuring incorrectly.

Measuring across R23 should give you around 44-50 volts, so the voltage is correct, but the AC measurement could be wrong;  there would not be this sort of AC voltage there at no signal UNLESS your earthing was way off and you have massive earth hum.  Measure the AC again;  it's more likely to be 109.3mV of AC.

When you measure R26b and R27b you should measure across EACH one, not the two of them.  Both tubes run near identical operating points, so you are actually measuring only the discrepancy between them.  Try measuring across R26b - should be 44-50V - and the same for R27b.

RIGHT CHANNEL

Across R12 1.28v
o/p to gnd 0.9v
across R8 0.62v
across R4 1.545v
gnd and R12 14.09v
gnd and R8 -13.86v

Across R31 33.3v
gnd to R31 141v
*** gnd to R23 47.6v(dc)
*** across R26b-R27b 0.2v

Same comments for this section, Nick, you have a fully functioning SS and tube section here too!  Just remeasure R23 again, check it's 44-50 volts, and then across R26b and then R27b.  Both should be around 44-50V also.  The sections of this tube are showing tighter tolerance, but this is not critical as balance here is not required.

Congratulations!  Nearly there......

Cheers,

Hugh

[Grumpy_Git]

Can I have one final explaination for the GK1r earthing, I'm feeling particularly stupid right now and I didnt understand it before so I've got no chance now.

What I understand so far is that link 1 on the relay pcb is not required but I should run a twisted pair of cat 5 from to two holes next to Rm to somewhere on the Analogue board, my question is where, would a 0v pin off the 17-0-17 supply be acceptable?

Is this all that is required?

After that I just need to wire the pot/analogue and relay boards together, shouldnt be too hard, except im nearly out of cat5

Nick.

ps in steps 39 "connecting the left and right tube input to the mute/sub pins" and step 40 "attaching level control. Do the wires from the wiper on the pot and the wire from the relay board both connect to the same pin on the analogue board labelled wiper from output.

[Grumpy_Git]

Forget all that rubbish from the last post, I've wired everything up and theres a problem.

I only get music out of 1 channel (the right), I've swapped tubes and interconnects so its not those.  Any suggestions please before I go mad?!

Cheers.

Nick.

edit.  All values re-tested and are approximately the same, so nothing seems to have gone wrong electronically

[Grumpy_Git]

just leant on the ht button by mistake and the left speaker all but exploded with a loud distorted output.

I dont remember if there was an output from the right channel and dont want to check again!

We could be getting somewhere, any suggestions?

All the wiring looks the same.

Nick

[AKSA]

Nick,

For testing purposes, keep off that HT bypass button!!

Select CD or DVD, and stick to that.

REVISED GK1-R EARTHING SCHEME
(Use only if hum is serious!!)

Complete one channel first, THEN the other to avoid confusion.  Follow these steps for interconnections:

1.  Input pcb (source side, between RLY2 and RLY3) to analog pcb INPUT of SS section.  This one has the earth connected to both input pcb and the analog pcb at the GND connection under R2.

2.  Output from SS section (at ends of analog pcb) to motorized potentiometer.  Note the earth on the pot.  Earth is common to both channels, and should be connected ONLY at the pot end if you are using coax (recommended).  Don't connect the earth on this line to the analog pcb.
NB:   Don't fit the LINK just under C8.  This wiring scheme precludes it....

3.  Now run a connection using coax from the wiper on the pot (centre termination) to the base of C19 where it says 'Wiper from Attenuator'.  The earth braid (also called the 'shield') connects to the earth on the pot at one end, then the earth under R17 on the analog pcb.  Do not fit R17 (47K);  it's not needed.

4.  On the input pcb, remove LINK1, immediately above CONN2B.  You will earth the right side, output, in the next step.

5.  Now connect the output from the tube section on the analog pcb to the input pcb, just above RLY7.  The shield connects on the analog pcb to the outside of R18 (the 'earthy' side nearest C7), and on the input pcb to a point midway between RLY6 and RLY7.  You must drill a hole between the relays into the ground plane, and scratch sufficient silkscreen off the pcb to solder in a thickish wire or pcb pin.  This is the best attachment point for the ground termination on the output side of the input pcb.

6.  Now fit a 1K resistor in place of LINK1, but do not use the hole closest to RLY5 for the left side;  rather, use another hole just above it and connect the left side of this resistor to the curving track which comes off pin 1 of CONN2B.  This is the +5V buss of the relay power supply. and the purpose of this resistor is to reference the relay power supply to ground, so it does not float, causing hum intrusion.

7.  Run two thick copper wires from the earth point on the volume control to the left channel earth and the right channel earth ON THE ANALOG PCB.  The best point to connect is the junction of R26a/b and R27a/b, so it's best to attach it directly below the centre of the tube socket, and scratch away the silkscreen to allow soldering.  You can also drill a hole and use a pcb stake, but in most cases constructors will be mounting the pcb upside down, tube socket uppermost, so soldering to this land is easy.

8.  This is the test point for the preamplifier.  Test everything.  Mute will not work yet, however, as this is the last step.  

9.  If all checks out, now run a shielded wire from the potentiometer wiper (centre terminal) to the two pcb 'mute' stakes atop RLY6.  There's no need to earth the braid at the input pcb end;  but it must be connected to the potentiometer ground at theother end to prevent hum induction.

This is the definitive earthing for the GK1-R.  It does NOT apply to the GK1-M, which is very easy to build without hum difficulties.  The reason the R is difficult is because of the huge additional complexity of the logic circuitry and relay switching - a design aspect not shared with the EL and M versions.  I can assure everyone here that the R can be made as quiet as a churchyard, but correct earthing requires a deal more attention to detail.  The existing earthing regime is often quite OK, but in some instances there has been stubborn hum, and the above approach trounces the problem 'soundly'.  

Nick, if you continue to have difficulties, take a deep breath and stare out the window for five minutes, then email me.  I'm delighted to help, and I promise you this will be fixed.

Cheers,

Hugh

[Grumpy_Git]

hugh my thanks, i'll have a look 2moro but i wanted to point out that i was getting acceptable music out of the right channel with a small amount of hum but i wasnt that bothered as there was no signal being output through the left channel, this surely isnt an earthing problem? thats why i mentioned hearing sound when i accidently pressed
 the ht bypass button-noise from the left channel!

off to bed now as its half one in the morning.

Nick

[Grumpy_Git]

Hugh / someone

for the 1k resistor to replace link 1 in your instructions above. could i get away with 1.5k as im out of 1k and cant get to a shop for 2 weeks.

cheers

Nick

[AKSA]

Nick,

1K5 is fine, its purpose is only ground referencing so any value to 100K is quite acceptable.

Progress?

Cheers,

Hugh

[Grumpy_Git]

Hello all, gk1 is working fitfully now, a bit of work and the she'll be fine.

I just wanted to know if anyone knows where I could buy female equivalents (sockets) of the pcb pins, this would make my life easier as I seem to spend a lot of time soldering, desoldering etc and these sockets would be useful in the assembly stage and could be soldered permanently once everything is working and in a case.

Cheers

Nick.

[Occam]

Nick,

If the pcb pins you're referring to are the same as on the Aksa amps, the removeable female sockets used in many computer connections, DB9/12/25 connecters work quite well. The male pins used in these DB connectors are 1mm round, which are quite similar to the pins that Hugh uses.
http://www.rsaustralia.com/
simply do a search on 'd socket'

FWIW

[AKSA]

Thank you Paul,

This is REALLY useful information, much appreciated!  

Cheers,

Hugh

[Rom]

Nick,

Paul's suggestion is right on the money, I have used them, but you may have to sleeve them with shrink tubing to have some insulator around them and to  make it more rigid some of the socket comes with a slit and they are a bit, I would say fragile as they are ment to be used with the D shell housing.

cheers
Rom

[andyr]

Nick,

Paul's suggestion is right on the money, I have used them, but you may have to sleeve them with shrink tubing to have some insulator around them and to  make it more rigid some of the socket comes with a slit and they are a bit, I would say fragile as they are ment to be used with the D shell housing.

cheers
Rom

BRILLIANT suggestion, Rom ... to put heatshrink round the socket!  

I have been using RS "pin sockets" for a while but was always concerned about the "grippy-ness" of the sockets.  With heatshrink, there will be absolutely nooooo problems!

Thanks,

Andy

[Grumpy_Git]

Evening Everone.

Sad I know but I've just removed my last croc clip and resoldered a pile of joints and now my GK1 works without any help, now I just need to case it up.

Any suggestions anyone (remembering that I'm currently poor)

cheers everyone.


Nick