[Rom]

Hi stvnharr,

Don't panic, No light's on LED do not mean no power on the trannies.

Do you have Heater on the tube, filament ?

If you do then there power there. if not then , check if you have the main AC power coming to your trannies by Voltmeter.

I hope this help.

cheers
rom

[stvnharr]

Rom,
AC fuse is okay.  Tubes are on.  But that's it.

Steve

[AKSA]

Hi Steven,

Hmmm.  Check:

1.  Power trafos, both of them, for 15Vac on the low voltage pins, taken wrt the 0V (center tap).

2.  Power rails of the SS section.  If the LEDs are not glowing, there's a good chance this is the culprit;  you can measure this voltage wrt ground on the pcb across the two zeners, THEN at top of R12, and bottom of R8.

3.  The voltage at the B+ of the tube wrt ground.  Best place for this is the left of R31, and the right of R31'.

This will tell us where the voltage has gone missing.  Sorry to hear of your problems.

Cheers,

Hugh

[stvnharr]

Back in action, me that is, this morning.

Three measurements
1. Couldn't seem to get much across the 0V and 15V pins from trafos

2. Gnd to top of R12 - 15V, so good
    Gnd to botm of R8- 10V, okay, I guess

3. Gnd to left of R31  - 147V
    Gnd to rightof R31' -148V

So, tube section seems okay
SS section has some voltage.  To get good voltage at R12 & R8 I have to have voltage from the trafo's, correct?

I have 15V Gnd to output pin.

I can go down to DSE and get a couple LED's.  But I won't install them until I get your reply.

Steve

[AKSA]

HI Steve,

Ground to bottom of R8 is low at just 10V.  It should be between 14.4 and 15 volts.

Can you check ground to bottom of R16.  It should be 15-16 volts.  Also, measure off ground to bottom of D6/D7 (which is also negative of C16).  This should be around 20-23 volts.

The fact that the LED is not working worries me too.  This should still be working even if the negative rail is low.  You might have to do a service call to Rosanna!!

Cheers,

Hugh

[stvnharr]

Hugh,
Left Channel
1. GND to bottom of R16 - 17.7
2. GND to bottom of D6/7 - 17.8V

Right Channel were both at 18 V

Redid Gnd to R8:  Left still around 10V
                           Right has the missing 5V, as it's around 5.4V

Steve

[AKSA]

Steve,

I think T6 is gone, and possibly the zener, Z2, too.

What is the offset at the bottom of R10/11, Steve?


Cheers,

Hugh

[stvnharr]

Steve,

I think T6 is gone, and possibly the zener, Z2, too.

What is the offset at the bottom of R10/11, Steve?


Cheers,

Hugh

Voltage GND to R10/11 is 15V Left
                                    14V Right

[AKSA]

Steve,

These figures conflict;  left is faulty, right is OK as I understand it.

Left should be at rail, + or - depending on what has failed, while right should be +/-5mV, no more.

It's looking as though you'd better bring it over for surgery!

Cheers,

Hugh

[stvnharr]

Steve,

These figures conflict;  left is faulty, right is OK as I understand it.

Left should be at rail, + or - depending on what has failed, while right should be +/-5mV, no more.

It's looking as though you'd better bring it over for surgery!

Cheers,

Hugh

There are a lot of things in conflict here!!!
After rechecking some measurements:

Left channel:  + rail to R12 is 16V; across Z1 is 16V; LED is NOT ON;  Current between R13/L1/T4 is 15.6V; between R13/14 is 7.8V.  Current Gnd to R11/T4/output is 15V

Right channel: + rail to R12 is 14.6V; across Z1 is 15V; LED is NOT ON;  Current between R13/L1/T4 is 13.5V; between R13/14 is 6.7V.  Current Gnd to R11/T4/output is 14.6V.

Left Channel: - rail  to R16/Z2 is 17.6V;  current across Z2 is 17.4V;
to R8 is 11.7V; to R9/10/11 is 15.5V.

Right Channel: - rail to R16/Z2 is 18.1V;  current across Z2 is 17.6V;
to R8 is 5.1V; to R9/10/11 is 14.2V;

Just retook these several times to get things correct.

Happy to come down for a visit.  Bring just the board?


Steve

[AKSA]

Yes, Steve,

tomorrow would be just fine, morning or afternoon is OK, let me know when by email!!

Sorry about this..... just bring the board.

Hugh

[stvnharr]

Yes, Steve,

tomorrow would be just fine, morning or afternoon is OK, let me know when by email!!

Sorry about this..... just bring the board.

Hugh

Hugh,
I'll send you an email shortly.  Tomorrow morning looks good to me.
Now to go book the dead cd player into the shop.

Steve

[stvnharr]

Hugh,
The story continues.  Cd player returned today and worked, sort of!
Turned on music and one channel wasn't too loud.  
***** Turned on the little cd player and got a very loud hum in one of the channels.  Little cd player thru amp all is okay, so problem in GK-1 again.  No doubt caused by something not right in one channel of cd player, another story.

I'm very practised at measuring now.  Everything measured good EXCEPT offset in offending channel is high at 33-35mv.  Tracing things back as best I can, looks like T3 went, and maybe T6.  Everything on + rail measures same as on good channel.
All the measurements across R12 and R16 looked good.

Does this make sense?

Steve

[AKSA]

Steven,

this is bad news.  What is:

1.  Voltage across R8.
2.  Voltage across R12.
3.  Voltage across R16.
4.  Voltage across Zener Z2.
5.  Vbe of each of the two input devices (red probe atop T6/R7 and black probe bottom of R9 (T2) then bottom of R1 (T1).

This will fully measure off the SS section.

Cheers,

Hugh

[stvnharr]

Hugh,
Sorry for the long delay.  I was promised to attend the local movies this evening, 6pm show, so had to leave just as I posted.

I've now returned, much calmer I might add.

I can duly say that I panicked too soon!!  The hum was a true mystery.  I must have had the plug on the little player not fully seated, as the hum was a real ground hum, loud too.  This has happened before, but I must have been calmer and saw the trouble right away.

However when I did all the measurements everything was fine except for the highish offset at 33-35mv.  All other voltage readings were as they should be.

Now, I've plugged things back up and the GK-1 is fine.  I made sure the plug on the little player was fully seated, and all played fine.

As I recall last Thursday one of the channels did have a highish offset, though I don't believe it was 35mv.  Is that offset reading liveable?  OR should we try to find a way to lower it?

Now I'm just pleased that it all works.

Of course the cd player has to go back to the shop with a low output in one of the channels.  But the other 4 channels are all fine so didn't wipe anything out, as I'd feared.

I'll sleep good.

Steve

[AKSA]

Ah, Steve,

Good news indeed!

The offset is high, and I'd check all other voltages are OK, particularly base/emitter on the diff pair - which should be the same within 5mV - but yes, as long as there is no crackling sound on the volume control as you move it it's livable and won't affect sonics.

Cheers,

Hugh

[stvnharr]

Steven,

What is:

1.  Voltage across R8.
2.  Voltage across R12.
3.  Voltage across R16.
4.  Voltage across Zener Z2.
5.  Vbe of each of the two input devices (red probe atop T6/R7 and black probe bottom of R9 (T2) then bottom of R1 (T1).

This will fully measure off the SS section.

Cheers,

Hugh

Hugh,
Okay, I just measured voltages to be sure:
1. Across R8 - .626v
2. Across R12 - 1.268v
3. Across R16 - 5.6v
4. Across Z2 - 15.53v
5. R6/7 to btm. R9 - .591v
    R6/7 to btm. R1 - .590v
6. Offset - 36mv

The other channel were essentially the same other than across R16 was 4.8v and voltage at top of R16 was .8v lower than other channel

Offset was 5mv.

There's no noise in changing volume and sound is okay.


Steve

[AKSA]

Steve,

Is offset positive or negative wrt ground?

What is the positive rail voltage at the top of R12 wrt ground?

This will clinch it - all other values are within spec.

Cheers,

Hugh

[stvnharr]

Steve,

Is offset positive or negative wrt ground?

What is the positive rail voltage at the top of R12 wrt ground?

This will clinch it - all other values are within spec.

Cheers,

Hugh

Hugh,
I'm back now.
Positive rail voltage at top of R12 is--------------------- 14.58v wrt ground.
Offset is---------------------------------------------------- +35mv wrt ground.

FYI on the "good" channel the offset is negative 3.0mv wrt ground.

Steve

[stvnharr]

Steve,

Is offset positive or negative wrt ground?

What is the positive rail voltage at the top of R12 wrt ground?

This will clinch it - all other values are within spec.

Cheers,

Hugh

Hugh,
I'm back now.
Positive rail voltage at top of R12 is--------------------- 14.58v wrt ground.
Offset is---------------------------------------------------- +35mv wrt ground.

FYI on the "good" channel the offset is negative 3.0mv wrt ground.

Steve

Hugh,
So, is all well now?
I hope so!!!!

Steve