gofar99 wrote:
Hi. you don't need two meters, but they are helpful if both are equally accurate. Just add both initial values together to get the actual current (the calculated values are usually not exact). The divide by two and set one side to that value and check the other afterwards. Make slight adjustments as needed. +/- about 2-3% difference is what you seek. Up to about 5-8% still good, above that an adjustment is indicated. After the initial power on recheck the settings after an hour or so. New tubes and components will drift a bit at the start. I like to recheck new builds about a week to a month later. Then only about every six months or so. I find if they are close at the end of week's use they are likely to be fine for a long time. I test my amps with a diy dual meter. I got two of the $10 digital 0-1 volt meters that run on 9 volt batteries. You need two separate batteries as there is no common point between the two circuits under test. Just a DPDT switch to turn the meters on and off and some jacks for probes. The batteries last forever, mine have lots of use (I am always building and testing amps) ....roughly 7 years now.
Good listening
Bruce
Hello I' am new in the forum, and I am very pleased to be here.
I am trying to build the Poddwatt series 2 and I have some question to ask for.
Q1 The 10uF cap is both to the two channels and is only one? And there are preferences about it? I have chosen a Mundorf oil cap
Q2 Does it matter if I use a output transformer fixed to 4 ohm?
Q3 The heater circuit, pins 9 of the 5751 valves are floating? (it's the center of the heater)
Q4 The DC reference for the heater circuit can be taken from one of the two 200V regulator? Or I have to make a third regulator?
Q5 The SSL, what is purpose? I don't understand the purpose of 3 led in parallel, and is not recommended to add a backverse diode in parallel to each led? to reduce reverse current
Q6 For the power supply I am ordering a PCB, is recommended to do the same with the valve circuit?
Q7 The ground buses, I ground all the components of the power supply and the I connect it to the anti ground loop, I ground all the signal components, and then I tie them both together at the input connection?
Q8 As potentiometer a 100+100K by alps is good? (I don't know this brand)
Q9 The only connection that have to be made with shielded wire are, from jack to potentiometer (I don't need more inputs), and then to the potentiometer to the board?
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) or 40 millivolts? The one is fine the other is quite horrible. If it is 40mv, then that circuit is working OK. I suspect that is the case as the cathode to ground voltage is correct. So....you have a problem somewhere else. The tubes are probably just fine or the values would be off. They are durable and don't suddenly fail like this. You need to go through and check for some connection that is missing or has a bad solder joint. make sure you didn't accidently ground the output terminals or for that matter the input ones. Check to be sure the drive tube is functioning properly. Measure the voltage at the coupling capacitor on the driver tube side. It ought to be about 1/2 the B+ give or take up to 25%. If not then you have located the problem stage. If it is OK then you have some sort of signal issue. Either none going into the stage, none getting to the output stage or none gettin past the transformer. 