Pass Pearl trouble shooting

[deepak]

I noticed a channel imbalance in my Pearl phono. It appeared out of the blue, was working fine up until a few days ago. Anyone have any suggestions where to begin trouble shooting?

 

Does anyone still have the schematic/build PDF? Pass DIY site only has the Pearl 2.

 

It is the phono, I've isolated every other component including the cartridge. And I'm getting perfect channel balance with another stand alone phono.

[luvdunhill]

Measure the voltage drop across the four 22 ohm resistors that degenerate the four input 2SK170 to start with. Also the 10 ohm near the 2SK389. Compare channels.

Edited January 9, 2014 by luvdunhill

[luvdunhill]

I have the manual just can't upload it from my phone to Tapatalk and I am lazy. PM me your email addr.

[deepak]

Thanks Marc, will do that. The PDF was still up on their site, just not posted anywhere. Found it from

[luvdunhill]

If one of the SK170 is bad (my guess) I can match a new one for ya.

[The Expanding Man]

Can I ask your opinion on this phono stage?

 

It's on my list of possible upgrades.

 

I've got bugger all prospects of auditioning round my neck of the woods.

[deepak]

Thank you Marc, I'll get to this in a week or so.

 

EM it's a really great phono, I have had mine for a long time. With my 2.5 mv cartridge there wasn't much difference between it and a retail Ono. I am using a NAD PP-2 as backup and just from a couple of hours listening last night I am missing the Pearl. I am going to build Salas' Valve Itch next (w/o stepup)

[deepak]

Measure the voltage drop across the four 22 ohm resistors that degenerate the four input 2SK170 to start with. Also the 10 ohm near the 2SK389. Compare channels.

107 mv drop across each of the 22 ohm resistors in both channels. Across the 10 ohm resistor 118 mv in right channel, 290 mv in left channel

[luvdunhill]

Likely the expensive one in the right channel went bad I can verify when I can grab the schematic.

Edited January 24, 2014 by luvdunhill

[deepak]

Likely the expensive one in the right channel went bad I can verify when I can grab the schematic.

I think you are right, the 10 ohm is the ballast resistor for the 389 :/

[deepak]

The PDF says to use BL, but I found some 2sk289-GR from an old BDent order (thank you hoarding), would it be ok to replace these in both channels?

[luvdunhill]

I would replace the bad one first and go from there.

[luvdunhill]

Sorry I wasn't clear. Replace the bad one and compare the voltage drops across the 10 ohm resistor. They will be close but not exact. You can then adjust the ballast resistor (you can do this out of circuit, since you have a board to get the voltage on top of the jfets from, also it is on the schematic) and then make the same change on the good chanel. Or just replace them with matched singles K170BL. Or negotiate a trade I might have some lying around.