Version 3.2
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***SAFETY WARNING READ THIS FIRST!!!!!***
Working Inside A Tube Amplifier Safely
Working inside a tube amplifier can be dangerous if you don't know the basic safety practices.
If you aren't prepared to take the time to learn and apply the right precautions to keep yourself
safe, don't work on your own amp. You can seriously injure yourself or get yourself killed.
Unplug
Pretty self explanatory. Do not, ever, ever, leave the equipment plugged in and start
work on it. Leaving it plugged in guarantees that you will have hazardous voltages inside the
chassis where you are about to work.
Sit
If the amp has been turned on recently, the caps will still have some high voltage left in
them after the switch is turned off. Let it sit for five minutes after you turn it off.
Drain
When you open up an amp, you need to find a way to drain off any residual high
voltage. A handy way to do this is to connect a shorting jumper between the plate of a preamp
tube and chassis ground. This jumper will drain any high voltage to ground through the 50k to
100K 2W plate resistor on the tube. To do this successfully, you will need to know which pins
are the plate pins. Look it up for the amp you're going to be working on. You'll need to know
this for the work anyway. Leave the jumper in place while you do your work. Remember to
remove it when you finish your work. You can also permanently install a 220K 2W resistor on
the B+ line to chassis ground to do this.
Test
Take your multimeter and ground the negative, black lead to the chassis. With the
positive, red lead, probe the high voltage cap terminals or leads and be sure the voltage across
them is low. Preferably to less than 10V.
Close
First take the shorting jumper out. Put the chassis back in the cabinet, making sure all of
your tools, stray bits of solder, wire, etc. are out of it. You don't have to actually put all the
screws and so forth back in if you believe more work might be needed, but make sure that the
chassis is sitting stably in the cabinet and won't fall out.
First note that most meters have three input jacks (some have four) one is marked COM, the
BLACK lead goes there. Another jack is marked V, ohm, mA, the RED lead goes there for
most measurements. The third jack is a high current jack usually marked 10ADC (sometimes it
is 20 or some other number). This jack is used only for high current measurements. The four
jack models use separate jacks for current measurements, this makes accidentally setting the
meter to a current mode harder, but it still can be set to resistance. For vacuum tube
electronics we can usually ignore the high current mode. Put your test leads into the COM and
V(ohm)mA jacks and leave them there.
Summary of Contents for Trinity Tweed Amp
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Page 20: ...Version 3 2 Page 20 Input Jack Theory from 18watt com ...
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Page 65: ...Version 3 2 Page 65 HEYBOER OT for TWEED 6L6GT CONVERSION ...
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Page 77: ...Version 3 2 Page 77 Trinity Amps Schematics and Layouts ...