Hi,
I'm checking this thread weekly or so for updates, because I'm still repairing my russian L3-3 and well, it doesn't work right yet.
So far I've replaced all paper capacitors, one of these odd wire wound resistors and the -ug1 10v potentiometer. I couldn't source suitable resistance wire, so I've fitted two 1% 1w resistors in parallel with a normal 1/4w 1% resistor as a replacement for the original soviet resistor. So far I'm able to make somewhat reliable measurements of the anode- and screengrid currents and it is also possible to get a mutual conductance reading.
However I'm unable to make either Ig1 readings or leakage measurements. It's almost impossible to get the µA-meter calibration right and so far I haven't been able to find any error with the amplifier circuit. I suspect that the wire harness might have poor insulation somewhere, but unfortunately it is a bit difficult to spot this type of fault.
I will build a replacement for the network R93-R99 using normal resistors and maybe then I'll be able to get the µA-meter calibration right...
I'm checking this thread weekly or so for updates, because I'm still repairing my russian L3-3 and well, it doesn't work right yet.
So far I've replaced all paper capacitors, one of these odd wire wound resistors and the -ug1 10v potentiometer. I couldn't source suitable resistance wire, so I've fitted two 1% 1w resistors in parallel with a normal 1/4w 1% resistor as a replacement for the original soviet resistor. So far I'm able to make somewhat reliable measurements of the anode- and screengrid currents and it is also possible to get a mutual conductance reading.
However I'm unable to make either Ig1 readings or leakage measurements. It's almost impossible to get the µA-meter calibration right and so far I haven't been able to find any error with the amplifier circuit. I suspect that the wire harness might have poor insulation somewhere, but unfortunately it is a bit difficult to spot this type of fault.
I will build a replacement for the network R93-R99 using normal resistors and maybe then I'll be able to get the µA-meter calibration right...
Hi Alex,
Have you followed the steps of checking the Ig1 and Ileak scales indicated in the manual? Where exactly did you stuck with uA-meter calibration?
Nice to know there's still some one working the same project with me
Regards,
Duong
Dear Duong,
I've tried to calibrate the µA-meter according to the german manual, but it is almost impossible to adjust both "0" and "calibration" to the respective desired values.
The manual suggests to adjust the potentiometer behind the door on the left side of the valve tester in case it is impossible to get the correct adjustment with the potentiometers on the front panel, but that doesn't help either, because it won't possible to either adjust the zero point or to get the meter to the triangular calibration point. However I did manage to finish the calibration procedures after some fiddling, but now the meter will only display arbitrary values that won't change if I insert a valve or not.
I've checked the voltages on the measurement amplifier and they all appear to be correct, if that part of the german manual is error-free...
I've read that the russian cabling is less than perfect and often leaky in another forum and for now I would like to get some reasonable readings from the meter, because I'm not that picky to rewire larger parts of the valve tester. After all the wiring looms are huge and I would prefer not to dissect them without a good reason.
@v4lve lover: So far I've replaced only the -10v potentiometer, because the carbon track had some really bad burn marks. The other potentiomers I've cleaned looked fine to me
and in my opinion it just isn't worth the hassle to replace these potentiometers with 10gang versions, because you get a -10v and a -65v range which covers about everything you'll ever test with sufficient accuracy.
I've tried to calibrate the µA-meter according to the german manual, but it is almost impossible to adjust both "0" and "calibration" to the respective desired values.
The manual suggests to adjust the potentiometer behind the door on the left side of the valve tester in case it is impossible to get the correct adjustment with the potentiometers on the front panel, but that doesn't help either, because it won't possible to either adjust the zero point or to get the meter to the triangular calibration point. However I did manage to finish the calibration procedures after some fiddling, but now the meter will only display arbitrary values that won't change if I insert a valve or not.
I've checked the voltages on the measurement amplifier and they all appear to be correct, if that part of the german manual is error-free...
I've read that the russian cabling is less than perfect and often leaky in another forum and for now I would like to get some reasonable readings from the meter, because I'm not that picky to rewire larger parts of the valve tester. After all the wiring looms are huge and I would prefer not to dissect them without a good reason.
@v4lve lover: So far I've replaced only the -10v potentiometer, because the carbon track had some really bad burn marks. The other potentiomers I've cleaned looked fine to me
and in my opinion it just isn't worth the hassle to replace these potentiometers with 10gang versions, because you get a -10v and a -65v range which covers about everything you'll ever test with sufficient accuracy.
Hi Alex,
Have you checked the diode D20, tube VL18, R119 & R123 as indicated in the manual (section 8)?
Currently I'm refining the English translation of the manual based on the original versions and my personal understanding, i will upload it when I finish. I hope this will help.
I'm also study the tester to creat new cards for other tubes
Have you checked the diode D20, tube VL18, R119 & R123 as indicated in the manual (section 8)?
Currently I'm refining the English translation of the manual based on the original versions and my personal understanding, i will upload it when I finish. I hope this will help.
I'm also study the tester to creat new cards for other tubes
Hello again,
I forgot to add that I've fitted a new set of tubes.
R123 is intact and the 100v supply (r119, vd20) seems to be working, there is a bit of ripple though, but I suspect that this is due to the rather small filtering capacitor C9.
There are lots of cards available for popular european tubes from: Arthur´s Technik- Seiten
You'll find a .zip file with the cards and required splan reader at the bottom of this page here:
L1-3 - Prüfkartenherstellung mit Splan
I forgot to add that I've fitted a new set of tubes.
R123 is intact and the 100v supply (r119, vd20) seems to be working, there is a bit of ripple though, but I suspect that this is due to the rather small filtering capacitor C9.
There are lots of cards available for popular european tubes from: Arthur´s Technik- Seiten
You'll find a .zip file with the cards and required splan reader at the bottom of this page here:
L1-3 - Prüfkartenherstellung mit Splan
Most of the cards can be used directly with the tester, but you will need an adapter for some of them, because the either the tester lacks the required sockets or because it's not possible to make the required connections.
The adapterbox used by Arthur rudolph is described on this page here:
L1-3 Adapterbox
However it is possible to test many popular tubes like ECC83 or EL84 right away without any additional hardware, but you will require the adapterbox to test EF89 and other small pentodes. The cards that will require the adapter usually say something like "Oktalstecker Adapter in Fassung 4" which translates to "insert octal plug into socket #4" and you find the prefix "A" before the socket number.
As somebody has already found out in this thread it is not possible to use these cards without the adapter. If you're lucky it just won't work or you will even short some of the internal power supplies.
The adapterbox used by Arthur rudolph is described on this page here:
L1-3 Adapterbox
However it is possible to test many popular tubes like ECC83 or EL84 right away without any additional hardware, but you will require the adapterbox to test EF89 and other small pentodes. The cards that will require the adapter usually say something like "Oktalstecker Adapter in Fassung 4" which translates to "insert octal plug into socket #4" and you find the prefix "A" before the socket number.
As somebody has already found out in this thread it is not possible to use these cards without the adapter. If you're lucky it just won't work or you will even short some of the internal power supplies.
Make new card for the L3-3
After some further study, now I can say making a new card for the L3-3 is not a very hard task. You only need to carefully study the manual, the schematic, the tube datasheet and do some pratices with the tubes that already have cards (try making cards by yourself then compare with the original cards).
I also found that the document Kurzanleitung für das L3-3 at Jogis's site is extremely useful, especially for one who wants to creat cards for himself. Unfortunately the guide was written in German, I will try to make another translation and post it here along with the translation of the technical manual.
Yes for some tubes surely there wont be enough options for pinout ect. so we will have to use an adapter box, and the site of ardh45 is a very good reference.
I also have some other ideas to help further exploiting this tester:
- Replace the 6П1П-ЕВ tubes of the Ua regulator circuit (VL1, VL2) with 6П14П-ЕВ/EL84 to increase the power of this circuit. Of course you have to rewire the pinout of these tube to do this.
- The regulator can supply higher voltages than the tester itself can measure, I think they can deliver 4-500V for anode without much problem. The matter is just that the tester can measure up to 300V only, hence we need to use external meter to do the job, but again this is not very difficult. With this, we can test higher voltage, higher power tubes like 300B, 6550, ГУ-50... in their true working conditions.
What do you think about these ideas?
After some further study, now I can say making a new card for the L3-3 is not a very hard task. You only need to carefully study the manual, the schematic, the tube datasheet and do some pratices with the tubes that already have cards (try making cards by yourself then compare with the original cards).
I also found that the document Kurzanleitung für das L3-3 at Jogis's site is extremely useful, especially for one who wants to creat cards for himself. Unfortunately the guide was written in German, I will try to make another translation and post it here along with the translation of the technical manual.
Yes for some tubes surely there wont be enough options for pinout ect. so we will have to use an adapter box, and the site of ardh45 is a very good reference.
I also have some other ideas to help further exploiting this tester:
- Replace the 6П1П-ЕВ tubes of the Ua regulator circuit (VL1, VL2) with 6П14П-ЕВ/EL84 to increase the power of this circuit. Of course you have to rewire the pinout of these tube to do this.
- The regulator can supply higher voltages than the tester itself can measure, I think they can deliver 4-500V for anode without much problem. The matter is just that the tester can measure up to 300V only, hence we need to use external meter to do the job, but again this is not very difficult. With this, we can test higher voltage, higher power tubes like 300B, 6550, ГУ-50... in their true working conditions.
What do you think about these ideas?
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Make new card for the L1-3 or L3-3
Hello, you are right, depending on load you can get higher output voltages then 300V. I do on my testings the voltage measuring with 3 external calibrated multimeters (Ua, Ug2, Ug1 or Uk with cathode resistor. I made for this some special connector plugs where I can aditionally plugin an external meter.
Its also easy mod for measuring heater current or external feeding for heater, I use it for some U- or V-Tubes which had 100 or 50mA heater current and voltages up to 110V.
Replacement of 6p1p with EL84: I dont think thats a big difference, both are noval tubes with 12W Pmax on anode.
There are two things ho limit max. anode voltage at higher currents:
- the inner resistance of rectifier tube (in my case 5Z4M)
- the inner resistance of the both parallel 6p1p in the anode voltage regulator
and think, this part you need for gm measuring...
If you are interested i can send you some schematics and pictures therefore.
best regards arthur
Hello, you are right, depending on load you can get higher output voltages then 300V. I do on my testings the voltage measuring with 3 external calibrated multimeters (Ua, Ug2, Ug1 or Uk with cathode resistor. I made for this some special connector plugs where I can aditionally plugin an external meter.
Its also easy mod for measuring heater current or external feeding for heater, I use it for some U- or V-Tubes which had 100 or 50mA heater current and voltages up to 110V.
Replacement of 6p1p with EL84: I dont think thats a big difference, both are noval tubes with 12W Pmax on anode.
There are two things ho limit max. anode voltage at higher currents:
- the inner resistance of rectifier tube (in my case 5Z4M)
- the inner resistance of the both parallel 6p1p in the anode voltage regulator
and think, this part you need for gm measuring...
If you are interested i can send you some schematics and pictures therefore.
best regards arthur
This won't be much of an upgrade in my opinion, because EL84 offer the same Pa as russian 6p1p. Nos russian 6p1p are inexpensive and readily available and I'm not sure if you will gain anything from this modification.
This is somewhat true, but I suspect that the used valve regulators have a high dropout voltage and since the filtering capacitors are rather small the HV needs to be that high to ensure stable voltages under all operating conditions
I've been told that the method used for measuring transconductance isn't very accurate when measuring low-mu triodes like the 300b...
The best part about the L3-3 is its versatility, you can test about every tube up to the size of an el34 in every parameter and you also will be able to test most parameters with larger tubes like the 300b, 6550 or gu50. Why not just use it like a pocket knife? I mean it even has a handle on top which allows you to take the tester to your friendly surplus dealer.
I wouldn't like to make bigger and more complex modifications to my L3-3, because I'm conviced that it will take a lot of time to get it right and it is also possible that the end result won't be as good as the starting point.
Should you ever be able to buy larger quantities of any used transmitter valves your best option will be to make a purpose-built rig to test these valves. After all building an adjustable 1000v 0,5A lab power supply from new parts sounds much more like fun than working on the innards of an ancient soviet valve tester.
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For me, main limits of this tester are:
- Unavaiable pinout/socket for some tubes: this can be solved by making an adapter box like you have mentioned
- Limited measuring scales: we can use external meters
- Can not test high power tubes, when I say "high" here it means tubes with Pa max up to 4-50W (300B, 6550 or EL156...) only, not those monsters like 6C33C or 845. These tubes are quite popular, and it will be wonderful if this L3-3 can test/measure the parameters of these tubes at (or at least close to) their working condition.
Unfortunately, the manual says that this tester can test tubes with Pa max up to 25W only, it means there will be limit in voltage and current supply ability. And actually it wont let us to measure voltages above 300V and currents above 150mA.
According to my opinion, the thing that need to be powered up the most is the Voltage regulator for anode circuit. The others PSU (G2, 250V, heater) can handle the job easily.
For the high power tubes as I mentioned, I think a PSU that can deliver 500V/150mA is enough. That's why I came up with the ideas of upgrading the Anode PSU and using external meter.
According to the data, the transformer has 2x430V/260mA, so supply 500VDC/150mA wont be a problem, we just need to help the regulator to keep the voltage from dropping down too much when high current is needed. As you have pointed out, the bottle necks are the low value filter capacitors, the inner resistance of the rectifiers (in those which use valves as rectifiers) and the pass devices (6П1П). Can we solve those issues by using bigger caps and stronger tubes? If 6П14П/EL84 wont help, then is there any thing can be used?
Any idea or suggestion will be much appreciated
Regards,
Duong
- Unavaiable pinout/socket for some tubes: this can be solved by making an adapter box like you have mentioned
- Limited measuring scales: we can use external meters
- Can not test high power tubes, when I say "high" here it means tubes with Pa max up to 4-50W (300B, 6550 or EL156...) only, not those monsters like 6C33C or 845. These tubes are quite popular, and it will be wonderful if this L3-3 can test/measure the parameters of these tubes at (or at least close to) their working condition.
Unfortunately, the manual says that this tester can test tubes with Pa max up to 25W only, it means there will be limit in voltage and current supply ability. And actually it wont let us to measure voltages above 300V and currents above 150mA.
According to my opinion, the thing that need to be powered up the most is the Voltage regulator for anode circuit. The others PSU (G2, 250V, heater) can handle the job easily.
For the high power tubes as I mentioned, I think a PSU that can deliver 500V/150mA is enough. That's why I came up with the ideas of upgrading the Anode PSU and using external meter.
According to the data, the transformer has 2x430V/260mA, so supply 500VDC/150mA wont be a problem, we just need to help the regulator to keep the voltage from dropping down too much when high current is needed. As you have pointed out, the bottle necks are the low value filter capacitors, the inner resistance of the rectifiers (in those which use valves as rectifiers) and the pass devices (6П1П). Can we solve those issues by using bigger caps and stronger tubes? If 6П14П/EL84 wont help, then is there any thing can be used?
Any idea or suggestion will be much appreciated
Regards,
Duong
Yes, I also have similar plans in my mind
I also agree that the best thing with this L3-3 is its versatility with everything we need in one box.
Otherwise, with the meters, lab PSUs, function generators and oscilloscopes on our table, we can totally be able to build a test rig for the big tubes.
The obvious solution would be to fit a third 6p1p or any other tubes that offer a higher Pa, however most valves designed for use in series regulators (6080, 6336, 6s33s, ...) are bigger and draw a lot of heater current that won't be available from the built-in transformer...
To be honest I'm not sure if there is enough free space for any additional components, but you might want to check how much filtering capacity you'll be able to cramp into the meter if you remove the original soviet capacitors. Ripple voltage will be smaller if you manage to upgrade the filtering and while this might enable you to get higher output voltages, the biggest drawback is that the series tubes will have to work much harder especially at low voltages & high currents.
It's not impossible to modify the tester, but you will have to make some calculations beforehand. All assuming that the mains transformer is up to the job...
For me, main limits of this tester are:
- Unavaiable pinout/socket for some tubes: this can be solved by making an adapter box like you have mentioned
- Limited measuring scales: we can use external meters
- Can not test high power tubes, when I say "high" here it means tubes with Pa max up to 4-50W (300B, 6550 or EL156...) only, not those monsters like 6C33C or 845. These tubes are quite popular, and it will be wonderful if this L3-3 can test/measure the parameters of these tubes at (or at least close to) their working condition.
Unfortunately, the manual says that this tester can test tubes with Pa max up to 25W only, it means there will be limit in voltage and current supply ability. And actually it wont let us to measure voltages above 300V and currents above 150mA.
According to my opinion, the thing that need to be powered up the most is the Voltage regulator for anode circuit. The others PSU (G2, 250V, heater) can handle the job easily.
For the high power tubes as I mentioned, I think a PSU that can deliver 500V/150mA is enough. That's why I came up with the ideas of upgrading the Anode PSU and using external meter.
According to the data, the transformer has 2x430V/260mA, so supply 500VDC/150mA wont be a problem, we just need to help the regulator to keep the voltage from dropping down too much when high current is needed. As you have pointed out, the bottle necks are the low value filter capacitors, the inner resistance of the rectifiers (in those which use valves as rectifiers) and the pass devices (6П1П). Can we solve those issues by using bigger caps and stronger tubes? If 6П14П/EL84 wont help, then is there any thing can be used?
Any idea or suggestion will be much appreciated
Regards,
Duong
build something yourself I'd say
you can make adjustable voltages from variac or inductance dimmer-controlled transformers .
digital panel meters to measure everything you want are around €10 each for decent ones .
afraid something blows up ? use a EZ81 or something simmilair as a rectifier when overloaded they limit the current .
shorts test . a neon bulb and a few resistors along whit a 3 pole 12 position switch go a long way in making a funke style test switch .
v4lve lover
Looks like I was over confident with this tester.
Today I tried testing the 6550 with AC heater and high anode voltage (400VDC) but unfortunately the anode voltage could not be regulated and always drop when I tried to conduct high current (80mA and above) by changing g1 voltage.
Seems the only way to increase the power of this regulator is to replace it with semiconductor regulator and using bigger filter capacitors
Today I tried testing the 6550 with AC heater and high anode voltage (400VDC) but unfortunately the anode voltage could not be regulated and always drop when I tried to conduct high current (80mA and above) by changing g1 voltage.
Seems the only way to increase the power of this regulator is to replace it with semiconductor regulator and using bigger filter capacitors
Hi hoangduongo and arhd45,
I am still hoping to get my tester working. It seems not to be exactly the same as the one that Klemkosky has so extensively helped with here. How can I tell which factory mine comes from, and what the differences in function are? One difference is that R46 is labelled R43 iin mine - its in the same place and does the same thing.
Mine is an L3-3 from 1977, all the preliminary checks work up to checking the return current where there appears to be no meter movement at all. Also on rectified current checks the last 300mA test where FSD reads 138 rather than 150, and the current is 277mA, like the thing is running out of steam??
Any advice gratefully received!
I am still hoping to get my tester working. It seems not to be exactly the same as the one that Klemkosky has so extensively helped with here. How can I tell which factory mine comes from, and what the differences in function are? One difference is that R46 is labelled R43 iin mine - its in the same place and does the same thing.
Mine is an L3-3 from 1977, all the preliminary checks work up to checking the return current where there appears to be no meter movement at all. Also on rectified current checks the last 300mA test where FSD reads 138 rather than 150, and the current is 277mA, like the thing is running out of steam??
Any advice gratefully received!
L3-3 does not work?
Hi Jazid,
please tell me what is not working at your l3-3. Is it only a steepness (Gm) metr problem or do you have generally a calibration problem with the in built meter?
Generally the 1977 L3-3 should be last edition with silicone rectifiers, zenerdiodes for voltage references in the stabilizer and primary switch on the main transformer. do you have a correct schematic and parts list for your device?
Best regards arthur
Hi Jazid,
please tell me what is not working at your l3-3. Is it only a steepness (Gm) metr problem or do you have generally a calibration problem with the in built meter?
Generally the 1977 L3-3 should be last edition with silicone rectifiers, zenerdiodes for voltage references in the stabilizer and primary switch on the main transformer. do you have a correct schematic and parts list for your device?
Best regards arthur
I've tested the µA according to the manual, that means the following connections were made: 2/I, 20/I, 26/I, 40/II, 52/II, 7/I
If I connect another 150µA µAmeter in series with a 68ohm resistor between connector 43/I and ground I'm able to get some readings when adjusting the -10v ug1 potentiometer. However I'm still unable to get consistent readings between the two µA meters.
I can adjust the internal meter to either match 0µA or 150µA, which means that if I adjust zero correctly it won't get even close to full scale if there is a leakage current of 150µA.
I've checked the divider network thoroughly - and no results (I got to see that movie once again...)
Kind regards,
alex5612
L3-3 Push to Test Switch
Hi
I have a L3-3 in good condition which I would love to experiment with, but my 'Push to Test' switch has self destructed.
It was purely a mechanical issue, no electrical problems.
I have been trying for ages now to find a new one.
Does anyone here have a spare or know where I could get one ?
I'm more than happy to pay all expenses and any reasonable price to get this beauty up and running again.
Here's hoping...
Hi
I have a L3-3 in good condition which I would love to experiment with, but my 'Push to Test' switch has self destructed.
It was purely a mechanical issue, no electrical problems.
I have been trying for ages now to find a new one.
Does anyone here have a spare or know where I could get one ?
I'm more than happy to pay all expenses and any reasonable price to get this beauty up and running again.
Here's hoping...