[dayneger]

After an embarrassingly long hiatus, I finally resurrected my GK-1R and put in a bunch of upgrades that've been recommended on other threads here.  Most things worked out, but I'm having a few issues that have left me baffled--I can solder things together, but I'm unfortunately pretty clueless about how my rig works!     Any suggestions would be great!

First, the modifications:

C1 changed to Sonicap Platinum 1uf (long lead to input end)
C19 changed to Sonicap Platinum 0.01uf
R13 changed to 470Ω
R14 changed to 10kΩ
T4 changed to matched BC560 from a group buy a while back
L1 and C4 swapped
C4 and C7 changed to Auricap 40uf caps

Did I miss any great upgrades? 

At first things fired up fine and the offset voltages were (shockingly enough!) running exactly within spec.  After 2 days I started getting intermittent fuzzing through one channel.  When the fuzzing was occurring I was measuring basically 0 volts across R12.  Rewetting all of the solder contacts on that side of the board settled the issue, much to my relief.

Then, I noticed that my remote volume and switching aren't working.    

Things I've tried/checked:
- Manual switching of all inputs and the mute/volume attenuation works fine, but using the remote does nothing
- I've repeated the remote initialization procedure a few times and it seems to work fine
- I've unplugged and replugged the flat connection cables at both ends
- The IR sensor is showing 5v, 5v, and 0v on the ground
- When the remote is sending a volume signal the output of the sensor shows a different voltage, so I'm assuming the IR sensor is working correctly (I don't have an oscilloscope)
- When the remote is firing, there is no voltage change in either AC or DC across the motor wires
- I've rewetted all of the solder connections on the digital control PCB, to no avail

Ideas on how to diagnose/correct this problem?

After working on the remote issue and getting nowhere, I decided to just enjoy some music, so I carefully remounted everything and... my right tube output now has bizarre behavior!   

The symptoms:
- First, running off of the solid state outputs works great.  Both channels are now (thankfully) fine--clear, full frequency, equally loud.
- Now, using the tube outputs, the right channel is letting a lot of signal through the tweeter even when the volume pot is set to 0.  The left is quiet.
- With the volume up, I'm getting literally no bass at all through the right channel, as though there were a high pass filter.  The treble volume also seems lower than that of the left channel.
- I swapped the tubes L-R and the problem stayed on the right channel.
- The input and output wires all seem to be attached

Again, any ideas about what might've gone wrong here?

Thanks!

Dayne

[AKSA]

DN,

It's been a while since I worked on one of these!!  9 years ago I released the GK1, the R version two years later!

Measure the voltage at the tube plates, to the left of R31/32 where it says 140V.  It should be 135-145V.

Then measure the voltage across R19, the one near C21.  It is 30K;  the voltage should be around 30V.

Then measure the voltages across the cathode resistors, R26A/B, and R27A/B, both should be 44-49V.

I'll deal with the remote last.

Hugh

[dayneger]

Hi Hugh,

Thanks for getting back to me!  Just got the channel part resolved--turns out a signal wire from the pot to the tube circuit had separated, although this wasn't apparent visually. 

I'm discovering that the solid core signal wires I used, which were the hot thing at the time, are pretty poor when you need to repeatedly pull your board to work on it.  Fortunately, that problem did just turn out to be a mechanical issue and not something more arcane--although I admit I have absolutely no idea why the system responded as it did, passing some high frequency stuff but no low frequencies!  Weird.

Sorry to trouble you with the remote part.  Do you also have a schematic of those 2 boards?  A friend of mine is a EE and willing to help.

It's raining cats and dogs here in the SF Bay Area!

Dayne

[AKSA]

Dayne,

No schematic, unfortunately, but essentially check the following:

#1  5V supply correct and connected to the IR sensor via the ribbon cable.
#2  Check remote is working properly with a 'learning remote', and check battery is good in remote.

If the push buttons are working fine, we can conclude that all is well with the uprocessor, merely the ribbon cable is up for suspicion, supply is broken, or, possibly there is something wrong on the remote button board with the IR sensor.  There's not much to go wrong, in fact.

Hope this helps, sorry for delay,

Cheers,

Hugh

[dayneger]

Hi Hugh,

Ok, I found the culprit!

Although the remote initialized properly and showed the LED while firing commands, and although the IR sensor output showed that it was responding to commands from remote, apparently the remote was sending junk due to low voltage.  Fresh batteries saved the day and everything's working properly now.

 

The caps are burning in and the rig sounds great!

Cheers,

Dayne

[AKSA]

Dayne,

This is VERY good news.  Flat batteries are a major issue for DMMs, too, with some very strange voltages measured on low charge!

Congratulations and happy listening!

Cheers,

Hugh