I heard from some techs when you need replace power valves It's advisable replace PI valve too. What do you think about It?
Some ones on PI position looks like suffer more stress.
You know what you test rig is showing, whereas I'm not sure.I built a ECC83 valve tester. I checked all my ECC83 valves. Some ones on PI position looks like suffer more stress.
yeah 6.3 megatons of the old bags’ hatred towards your favorite pastime. might need more tubes, (or break out that 100w).A: No. This is an "old wive's tale" propagated
This valve tester works prety same condicions as a valve amp. It has same power suply like a Madamp J5MK1. I did many test with ECC83/12AX7 valves. New ones, bad ones, balanced, etc... It test anode voltage and anode current on each triode. I test each triode with about 350Vdc. You can see on B+ display. You can see anode voltage on each triode on anode display using a toogle switch. I test anode current on each triode. I use this schematic from this youtube video where he explain It. He talks just about anode drop voltage on each triode but you know a drop voltage has relation with current. If not a drop voltage on anode no anode current. No voltage and current on cathode too. I realise If you have less than 1mA on one anode a valve sounds weak. A new ECC83 valve has about 1,25mA on each triode If you use this schematic. A balanced ECC83 has same anode current and same anode voltage on each triode. I tested many ECC83/12AX7. Current production ones and NOS ones. This tester don't show If a valve sounds good. It don't show If a valve it's noisy. It show how a valve is working. It show how fast anode get max current on each triode. A good condition valve quickly is working. A tired valve needs some seconds to show max current on each triode. You can see how quickly is a valve working with analog current meters. I can use a DMM to test current on each triode as well. I get a super acurated readings with a DMM. It has two toogle switch to open the circuit then you close the circuit using a current meter to get current readings.You know what you test rig is showing, whereas I'm not sure.
Can you explain what's being shown, and how analysis of the readings has led you to come to that conclusion?
I don't think most common LTP circuits put their triodes under particularly stressful operating conditions.
You are right. But with this tester I know and I can see why a valve sounds weak and I need replace a ECC83/12AX7 valve. I can know If a preamp valve it's ok faster than by turning on and playing an amp.Replace it when a new one makes the amp work and sound better. Every so often, try out a new one. If you don't hear a difference, put the old one back in and keep running it.
There's meters under the following labelsIt test anode voltage and anode current on each triode
HT voltage display show when HT voltage it's on. When it's on 257-259 Vca I know I'm testing at 230Vca. I use a variac and I use an isolated transformer with It. B plus display show valve suply. Anode display show anode voltage. If anode display voltage it's same like B plus display voltage on one triode I know this triode don't works.There's meters under the following labels
HTVol
B plus
ANODE
Could you explain what they're measuring?
I tested current production balanced valve from TAD(two). They show same anode voltage and same anode current on each triode. They are used phase inverter valves. Also I tested an older than me green logo Philipps ECC83 that tested great. This valve sounds awesome. Some current production valves I tested worn out really fast (7025 12AX7 from TAD) Less than three years of use on V1 position. I tested very used Marshalls ECC83 from '90s. Some ones still ok.I have a number of NOS and new current stock 12AX7, 12AT7, 12AU7 and a mismatch between the two triodes is the rule. The exception is when they are pretty close...which of course you can pay extra to get. So that needs to be considered when measuring a mismatch in a used tube. If you don't know 100% they were matched when new, which is improbable, then you can't jump to the conclusion that one side is taking more wear and tear when you measure the mismatch in a used tube.