Available in the RCA output PAS 0.3 VAC, brings Hum and electric differential jumping house.
The voltage scheme below.
Anyone know the problem?.
The voltage scheme below.
Anyone know the problem?.
3 posters
VAC Dynaco PAS
Pillo69- Posts : 176
Join date : 2012-04-11
Location : Granada (España)
peterh- Posts : 1869
Join date : 2012-12-25
Location : gothenburg, sweden
Voltages seems ok.
But i do not understand your question. What is the problem ?
And is this an unmodified PAS-3 ?
But i do not understand your question. What is the problem ?
And is this an unmodified PAS-3 ?
Pillo69- Posts : 176
Join date : 2012-04-11
Location : Granada (España)
Yes, it is an original PAS. 240v transformer rewind.
There is a leak that generates VAC HUM me, and when I connect to a device with RCA grounding differential rises from the house.
sorry for my english.
There is a leak that generates VAC HUM me, and when I connect to a device with RCA grounding differential rises from the house.
sorry for my english.
Roy Mottram- Admin
- Posts : 1838
Join date : 2008-11-30
pin 7 is a grid, you can't expect to be able to measure grid voltages with most meters, as they will load the circuit down
that's the huge advantage of an old fashioned vacuum tube voltmeter, which has 11 megohm impedance or great.
Most modern DVMs only have around 1Mohm impedance.
If you are getting hum, most likely your source isn't grounded the same as the PAS preamp, or there is a poor ground connection somewhere, or more likely a ground loop.
that's the huge advantage of an old fashioned vacuum tube voltmeter, which has 11 megohm impedance or great.
Most modern DVMs only have around 1Mohm impedance.
If you are getting hum, most likely your source isn't grounded the same as the PAS preamp, or there is a poor ground connection somewhere, or more likely a ground loop.
Pillo69- Posts : 176
Join date : 2012-04-11
Location : Granada (España)
tubes4hifi wrote:pin 7 is a grid, you can't expect to be able to measure grid voltages with most meters, as they will load the circuit down
that's the huge advantage of an old fashioned vacuum tube voltmeter, which has 11 megohm impedance or great.
Most modern DVMs only have around 1Mohm impedance.
If you are getting hum, most likely your source isn't grounded the same as the PAS preamp, or there is a poor ground connection somewhere, or more likely a ground loop.
The 0.3 VAC in the line-out are also due to that ground loop?.
Thank you.
Roy Mottram- Admin
- Posts : 1838
Join date : 2008-11-30
that's probably the hum you are hearing!
Pillo69- Posts : 176
Join date : 2012-04-11
Location : Granada (España)
I have replaced three Phono inputs wiring, I put OFC screened cable, the HUM is gone, but current over the mass still exists.
Pillo69- Posts : 176
Join date : 2012-04-11
Location : Granada (España)
I have replaced the PAS volume potentiometer with an ALPS (100 k) without loudness.
I have read in several places that the resistance of 4 k 7 is due to start. Where I put it?.
I have read in several places that the resistance of 4 k 7 is due to start. Where I put it?.
Pillo69- Posts : 176
Join date : 2012-04-11
Location : Granada (España)
Update the thread to show the solution shunt to ground voltage.
The problem was .02 capacitor next to the power switch. I used the tester and showed me the correct value, however as a last resort I've replaced and the problem is resolved.
The problem was .02 capacitor next to the power switch. I used the tester and showed me the correct value, however as a last resort I've replaced and the problem is resolved.