NOSValves

I've been using the shuguang made KT88SC formerly from Penta labs and now from Ruby tubes KT88V-STR for years. I've never tried the new "branded" Mullard but to date sonically I've never met a Russian made KT88 I liked. Although many of them are more reliable than the Chinese made KT88's. I wish all the high end jobs coming out of China didn't have the smoked glass I'd love to see the business end of these tube to see if they truly are any different...

Must of had to build up a boat load of gain to drive the phase inverter transformer. If that is the case they probably do make a pretty large sonic change brand to brand.

1st band Brown =1 2nd band Black =0 3rd band Black =X1 So 10 X 1 =10 Ohms 4th band Silver = 10% Tolerance 5th band Brown = voltage rating but I don't have a chart handy at the moment The only real way you can check the accuracy of the built in meters would be to unhook one of there wires. Than remeasure the resistor value and than measure the voltage on the resistor after the amp is warmed up. Use the ohms law to figure out what the voltage equates to mA wise. All pretty anal retentive since the meters have to be fairly close. The measurements you took so far are totally inaccurate and unreliable.

Yea but the screwy part is I've seen lots of these meter over the years and own a bunch of them myself both US and from the other side of the pond...I've never seen one have even close the 1 ohm of resistance.

What is the color bands on those resistors? It looks like its Brown/Black/Black which = 10 ohms not 1 ohm. I think your reading 1 ohm because its shunted off by the built in meter which has to have pretty low internal resistance. I'm shocked it has 1 ohm or more.... I've never seen one that wasn't at or real near zero. In the end as long as that built in meter is connected to the cathode you can not measure with any meter. When you measured .650 or whatever is was that was .650 of 1 single mA you can't pile meter on top of meter on top of a resistor. All 3 devices were splitting the current running through the tubes cathode. I believe the 10 ohm resistor is there to allow the tube to still work if the meter fails shorting open. The built in meter is shunting the 10 ohm resistor down to the single ohm so most of the current is running through the meter. As the Italians would say use the onboard meters and forgetaboutit.

But when you measure the resistance of the resistor on pin 8 of the output tubes it measures 1.2 ohm? I'm scratching my head big time here.... something is screwy.

Bonzo. I think in the end you're going to find that you'll have more issues with the lower rated pin compatible tubes you can use in VRD's like 6L6GC, 7581A and so on simply because those tubes are running near there maximum design center lines in the amps while the KT88/6550 family of tubes are running nice and easy.

Its been a while since I had a set of PCats here but I do not recall them using a quad of 12AX7's....maybe just brain fog on my part.

Do those meters have a button to activate them? Or do they always display the bias as shown in the pictures above?

See those are purpose built analog DC mA current meters which should have little or no internal resistance.. Can you trace back to the tube socket what pins they are attached to?

The meters I'm concerns with and wanted close up pictures of are the meters built into the amps. I want to know if they are reading current or voltage. Again Maynard is right your can not use the current reading function of your digital meter to accurately read the current across the cathode resistor. That resistor is place there sop you can read voltage and use ohm law to figure out the current just like you do on your other amplifier (or should be doing), I personally do not like to use a 1 ohm resistor because the voltage developed will be very small and subject the error especially with inexpensive meters. I'd much rather use a 10 ohm resistor

So let me get this right in my head. The two wires slide into the ends and butt up against that evidently low temperature solder in the center. Then you heat the solder and the heat shrink with the heat gun? Seams to me like the resulting solder joint isn't going to be super reliable. I guess I'm old school and would rather have a mechanical connection and then high temp solder...

Bump because it took me too long to find this thread after someone asked me about an item.

What are you setting the Klein to measure voltage or current?

Dave, Do you have a decent digital camera? If so take a close up shot of one of those meters. I wouldn't be surprised your measurement is more off than the meters. I again agree with Maynard (I think the red sea just parted) this is much to do about nothing .