Most of the valve testing that I do is as a routine part of the service and repair of valve amps. There is NO CHARGE for the testing of valves as a part of a repair and valve testing is included in every valve amp service. However I’m approached from time to time by people who just want valves testing either to sell or for peace of mind. Valve testing is charged per valve, the price depends on the service you require. There’s a minimum charge of £30 for valve testing when not performed as part of a service. There are 3 valve testing services currently available. Test certificates are available as part of all of the services. For large quantity valve testing requirements I’m happy to negotiate a reduced rate.
If you’re bringing me a repair and you have a couple of old valves you’d like me to test then no worries, that’s FOC and I can use them for the repair if they’re still good. If you’ve got a whole box, I may charge though!
Basic Valve testing (£5/valve)
Power tube testing
Basic octal valve testing is performed with a custom made octal valve tester. This tester gives anode current (also called plate current, sometimes labelled as Ip, Ia or even PC!) and transconductance (gm or TC) to allow the grouping of power valves into matched pairs or matched quads (or matched duodecads like this mesa boogie bass 400+ repair!).
Preamp tube testing
Dual triode preamp valve testing is performed on a Tube Imp valve tester, made on a very limited run here in the UK. If you’re testing a dual triode then it gives a anode current and transconductance for each triode, allowing you to determine if a valve is suitable for phase inverter duties. It’s not possible to test some valves on the basic service, these must be tested on the Avo test service.
We can perform the following tube tests:
- Heater filament test: Short circuit
- Heater filament test: Open circuit
- Heater filament test: Tolerance check
- Heater cathode insulation: Leakage
- Heater cathode insulation: Short Circuit
- Tests for heater current abnormalities
- Amplification factor
- Voltage gain
- Power gain
- Screen grid test
- Mutual conductance test
- Dual test for double triodes
- Emission
- Inter electrode leakage
- Inter electrode short circuit
- Flash-over (arc detection, high voltage breakdown)
- Gas ionisation test
Avo tube testing (£10/valve)
Basic tests are only suitable for noval (B9A) and octal valve types, some valves don’t fit into the ‘basic’ testing regime. For these valves we have a venerable AVO tester. Most commonly, we’re using the AVO test for valve rectifiers, but it can also test a wide range of valves with a wide range of bases. For valve types such as 7 pin, loctal, Duodecar, Rimlock etc, we use the AVO tester.
Advanced Valve testing (£10/valve)
This service uses a Ronald Dekker uTracer 3+ curve tracer. This is a digitally controlled curve tracer. This unit gives the following advantages:
- Anode (plate) current tracing
- Super accurate power valve matching at a range of realistic anode voltages
- Test any octal or noval valve
- Accurate Ia (Ip) value for a given anode and grid voltage
- Accurate transconductance (gm) calculation across a wide range of grid voltages
This is suitable for hifi customers and those wanting a greater degree of insight into valve performance.
Valve/tube types
We can test the following valve/tubes on the basic test (Datasheets available from http://www.r-type.org/):
Octal power tube testing (pentodes and tetrodes):
- EL34/6CA7;
- EL34L;
- 6L6;
- 6V6/6V6GTA;
- KT66;
- KT77;
- KT88;
- 6550;
- 5881;
Noval power tube testing (pentodes):
- EL84/6BQ5;
- 7819 (AVO service only)
- EL84-M
Noval preamp valve testing (dual triode):
- ECC81/12AT7;
- ECC82/12AU7;
- ECC83/12AX7;
- ECC99;
- 12BH7
Noval preamp valve testing (pentode)
- EF86 (AVO service only)
Valve rectifier testing (Advanced service only)
- 5U4GB (5U4G) (AVO service only)
- GZ34 (5AR4) (AVO service only)
- GZ32 (5AQ4 – CV593 – 52KU – 5V4G – 5Z4G) (AVO service only)
- EZ81 (6CA4) (AVO service only)
- 5Y3 (AVO service only)
Other tube testing
- 300B (AVO service only)
- 6SN7
- PX4
- U55
Other ‘basic’ testing (£10)
If your valve type isn’t listed then I can probably still test it, a basic or advanced test can be performed on nearly all the valves that are commonly available on valve amps from the late 1950s onwards. I also do a ‘basic’ test that checks basic function but cannot guarantee valve performance.
- Heater test: Apply the rated heater voltage to the filaments, check the current draw and ensure filaments are glowing.
- LV DC short test: Multimeter test to ensure that no pins (except filaments) measure a low resistance at DC. Low voltage, does not run the valves at rated anode voltages.
I’ve done these basic tests on:
MKT4/7 ( 7 pin Beam Tetrode) Sensibly equivalent to:- 7A2 – AC/Pen – APP4A – CV1683 – MP/Pen – KT42 – Pen4VA – A70B – N40 – P4VA
B65 (Octal Dual Triode) Sensibly equivalent to:- 13D2 – 6SN7GT – CV1988 – ECC32
B36 (Dual Triode) Sensibly equivalent to:- 12SN7GT – CV925
DL63 (Dual Triode) Sensibly equivalent to:- CV2912 – DH147 – 6R7G – OM4
U18/20 (Rectifier) Sensibly equivalent to:- 45IU – AU1 – CV1264 – FW4-500 – NU12 – FW4-800 – CV31 – 4/100BU – RV200/600
U50 (Rectifier) Sensibly equivalent to:- 5Y3G – CV1268 – CV3754 – 5Y3G/GT
L63 (Triode) Sensibly equivalent to:- 6C5 – 6J5G – CV1067 – CV1932 – VR67 – VT154
H63 (Triode) Sensibly equivalent to:- 6F5G – CV1073 – VT73