Can someone explain the 3 Harvard inputs?

[martin manning]

This is a puzzler, rp. I'd get the 1-meg and any jumper leads out of there, and insert a new 1/4" plug with no lead attached or a short 1/4"-1/4" cable into the #1. Maybe it's just the picture, but that homosexual thing looks like it might be a little tarnished.

Then, probe with your meter (on ohm setting) from the tip of the plug/cable to the tip lug of the jack, before and after the solder joint, and after the 68k resistor (where you should see 22.7k), and also from the sleeve of the plug/cable to the sleeve lug, before and after the solder joint.

Also check from the sleeve of the plug/cable to chassis ground. If that is not ~0, then step your way from the chassis ground to the plug/cable sleeve, checking both sides of each joint.

Re Cliff's comment, the 1-meg from #1 tip to ground will be shorted except when the #1 input is used, so #1 is the only input that has 1-meg to ground if the resistor is installed. That said, if the resistor is used, and a plug is in #1 (only), all of the jacks should measure 1-meg from tip to ground.

[rp]

Solved. Two bad jacks, apparently. Third's the charm. Hard to believe. Or one bad jack and one cold solder joint/flux bubble at the ground. Jacks test fine once pulled too, maybe the nut was too tight and they flex and go out of whack? I'm pretty diligent about this stuff, seems odd. And, no I didn't accidentally reinstall the same jack twice, I marked it w/ a sharpie the minute it came out before it left my hand. Habit from work so I don't mix up the old with the replacement - ever have that happen? Anyway, a real annoying gremlin in an otherwise 100% new amp.

Amp turned out flawless, dead quiet, voltages spot on to the schematic, sounds great, maybe amazing. A real firecracker w/o the typical 1M load resistor. You can immediately hear the fixed bias and NFB that it's not like a 5E3. Tweeds are all simply amazing. That smooth cone Tungsten gives it up pretty quick, I want to try a ceramic.

Housebound old lady in the next apt went apeshit on me yesterday. 3pm on a sat too! We are suppose to be friends. Granted who wants to hear a guy testing an amp out, playing chromatic bass notes and power cords listening for rattles? And I've been doing this a lot lately. Not sure how I'm gonna test my amps now.

I will unveil her on AG soon - the 5F10 not the old lady. Maybe after holidays.

Thanks all. Keeps lots of jacks handy.

[Structo]

Wow, crazy about the jacks.

The old lady, yeah well people are people and yes people don't like to hear you noodling no matter what time of day or night.

They just don't appreciate live music!

[martin manning]

Solved. Two bad jacks, apparently. ...A real firecracker w/o the typical 1M load resistor.

Cool! Interesting about the 1-meg... I guess the cable and p/u capacitance and inductance work some magic if the ground reference for the V1 grid goes that route.

[Dr-Joned]

[quote="Structo"]Wow, crazy about the jacks.

The old lady, yeah well people are people and yes people don't like to hear you noodling no matter what time of day or night.

They just don't appreciate live music! [/quote]

I hate to hear the boom, boom, boom from the passing cars either. But come to think of it, that's not music either!