Another example from Germany is the Klein and Hummel VS70 which used EL36s ...
K&H VS70
Sansui went the whole 9 TV yards in its 1000 ...
Sansui 1000
... which uses PL36s.
K&H VS70
Sansui went the whole 9 TV yards in its 1000 ...
Sansui 1000
... which uses PL36s.
Well, I had found three used EM85's in my shelves, and all of them sadly turned out to be even more dim that the really not too bright original UM85 indicator tube. One of them didn't show anything at all. Some search in the WWW showed that new EM85's are being offered for a whopping, breathtaking EUR 75 at least
!!! So, what to do? There's the PM84 indicator that shares the EM85 pinout, but is a more recent tube with a rectangular, linear display. Not acceptable for a '53 radio. So I went through my tube inventory and found a hand full of EM80's with a similar, fan shaped display like the U/EM85. I rewired the tube holder accordingly, rotated it by 144 deg so that the display shows to the glass dial and tried all my EM80's. Most of them were also dim, but I found one with a pleasing bright display that remains in the radio now. In addition, I swapped this tube's plate supply from after the filter choke to the 1st PSU capacitor so that it's supply voltage is increased from 220 to 240 Vdc now.As this radio doesn't feature a power transformer, but a hot chassis instead (like an AA5), it now sits in my garage with nothing ever getting connected to it.
Another observation: The new heater chain supply voltage is 68.3 Vac, but due to the phase shift the 4.3 µF series capacitor drops about 220 Vac. As the capacitor draws about 315 mA when directly connected to the 230 Vac mains, this means an almost constant heater current supply and a gentle, but prolonged warm-up time. Despite of this the »modern« PL82 warms up faster than the original, ancient UL41 power pentode.
Best regards!
Just thought I'd share some good fortune. At a recent swap meet there was a box labeled "free tubes". naturally I accepted! Most are TV set types but a few are radio or other types.
Bunch of 12AL11s, good sampling of TV types. Also some 6H6s, VR tubes 1625s, and unexpected a surprise tube of op-amp IC chips were in there. This isn't an ad, just a little celebration.
Bunch of 12AL11s, good sampling of TV types. Also some 6H6s, VR tubes 1625s, and unexpected a surprise tube of op-amp IC chips were in there. This isn't an ad, just a little celebration.
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It would be interesting to take that list and define a potential use for each one. I am trying to do that with my collection I have. All tubes are born equal, but some tubes are born more equal than others (I am sorry Mr. ECH81, but that is the way of the world).
This has been a great thread to follow but it would be nice to have some more talk about construction ideas, and maybe PCBs, to try and create a market for some of these tubes. I went through the thread again recently, and there was a lot of talk about sweep tubes for outputs, but it would be nice to find homes for the humbler tubes.
Actually, after singling out the ECH81 (or ECH83) here is a guitar effects pedal ...
Preamp/effect pedal
This has been a great thread to follow but it would be nice to have some more talk about construction ideas, and maybe PCBs, to try and create a market for some of these tubes. I went through the thread again recently, and there was a lot of talk about sweep tubes for outputs, but it would be nice to find homes for the humbler tubes.
Actually, after singling out the ECH81 (or ECH83) here is a guitar effects pedal ...
Preamp/effect pedal
The antique radio club of which I am a member also has those who like to build regenerative receivers the 'old way' (is there any other way?).
Most of those compactrons are attractive because they have 2 or 3 tubes in one envelope and one section can work up to 10 or 20 MHz.
Usually, regens have used headphones or had an output jack - do not always have an amp for driving a speaker, and some regens use two tubes to perform the required functions, and still have only a very low wattage output of 50-100mW.
The TV set ultor voltage rectifiers are useful un-lit as a high voltage capacitor in RF voltage dividers, and have been used as a neutralizing capacitor in ham RF radio power amps.
Most of those compactrons are attractive because they have 2 or 3 tubes in one envelope and one section can work up to 10 or 20 MHz.
Usually, regens have used headphones or had an output jack - do not always have an amp for driving a speaker, and some regens use two tubes to perform the required functions, and still have only a very low wattage output of 50-100mW.
The TV set ultor voltage rectifiers are useful un-lit as a high voltage capacitor in RF voltage dividers, and have been used as a neutralizing capacitor in ham RF radio power amps.
I've just converted my Jet City 2 x EL84 head to use 2 x PL83 TV tubes, I had some very old used Mullard '58 date codes PL83 in the junk box.
At the base of the socket jumper pins 1-9 and 6-3 for the EL83 (6,3v heater version) adjust the bias are you're good to go) Use a DPDT switch for pin3-6 if you want to switch between EL84 and EL83.
For PL83 we need a 15v/300mA heater supply, I just converted the 6.6v ac to dc and used a DC-DC buck booster and adjusted the multi-turn trim pot on the buck converter to supply 15v.
You loose a couple of watts but not really that noticeable, lots of mojo in those old Mullards can get them NOS for £5 each instead of £20 for a JJ EL84!
Doug.
At the base of the socket jumper pins 1-9 and 6-3 for the EL83 (6,3v heater version) adjust the bias are you're good to go) Use a DPDT switch for pin3-6 if you want to switch between EL84 and EL83.
For PL83 we need a 15v/300mA heater supply, I just converted the 6.6v ac to dc and used a DC-DC buck booster and adjusted the multi-turn trim pot on the buck converter to supply 15v.
You loose a couple of watts but not really that noticeable, lots of mojo in those old Mullards
can get them NOS for £5 each instead of £20 for a JJ EL84!Doug.
I’m attempting to collect data for various (successful) operatng points of EL83/6P15P used in amps intended for EL84/6P14P.
https://audiokarma.org/forums/index...of-a-6bq5-el84-6p14p-ev-in-my-pp-amp.1000253/
Could you kindly contribute and provide the operating parameters and circuit topology in your swap?
1. Is this amp pentode or Ultra Linear (Push pull assumed)?
2. What is the plate supply voltage, and screen supply (if not UL)
3. What is the control grid negative bias voltage, or the cathode bias.
4. What is the combined plate and screen current through each tube
5. What is the primary impedance (plate to plate) of the output transformer
6. What is the output power, at which speaker load.b
Here's some readings I did today, the PL83 valves are Mullard Blackburn plant 1958, used and untested from my junk box :
1. It's a consumer product guitar amp JCA22H, schematic of output section here:
https://www.diyaudio.com/community/...eplacement-and-minor-mod.329660/#post-5603824
2. HT supply:
OT CT is 377v
anode at V6 is 375v
screen at V6 is 360v
anode at V7 is 376v
screen at V7 is 359v
3. -ve bias at V6 grid is -8.03v and -7.94 at V7
4. at above -ve bias:
V6 anode to CT drop is 1.44v DCR of primary is 54.7Ω = 26mA
V6 screen resistor is 468Ω voltage drop = 1.69v = 3.6mA
V anode to CT drop is 1.03v DCR of primary is 43.1Ω = 23.9mA
V7 screen resistor is 467Ω voltage drop = 1.42v = 3mA
5. OT primary is 6.6KΩ into an 8Ω speaker - I wound this myself
6. Not measured power yet
Doug
Long before Svetlana ceased glass tube production, they published a technical bulletin that showed how to replace EL84's with their SV83 tube. I suppose that this tube originally was a 6P15P. They said it wasn't the same tube as a EL83 (or PL83), hence being called SV83, but I didn't recognize any significant differences in their data.
Best regards!
Best regards!
I have 4 x NOS Tesla 'Made in Czechoslovakia' to try next.
Also got some 6P15P = SV83
I ordered 2 x NOS Mullard PL83 for £5 each yesterday, can also get NOS Mullard EL83 for £7 each.
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The PL82 and PL84 are audio amp valves to start with so just need to get the 15v.
I've just tried the 4 Tesla PL83s and got them to match close enough for a guitar amp.
The 10 x 6P15P are another story...
Kay, If you recall where you saw this technical bulletin could you please pass on the link or source? Is it the same or different technical bulletin on this topic by Eric Barbour, issued after they started marketing the 6P15P in the US under the name SV83? The main differences between SV83 and EL83 are the pinout you mentioned and plate dissipation rating - 9 watt for EL83 vs. 12 watts for 6P15P, with small difference in screen dissipation rating.
VTV#14 has an article by Chris Beck about his “clone Dynaco ST35” using SV83 output tubes. He used a regulated 150Vdc supply on the screens and achieved 7.5 watts, which he felt sounded “far above” his SCA35.
https://worldradiohistory.com/Archi...m-Tube-Valley/Vacuum-Tube-Valley-Issue-14.pdf
I forgot to mention when using the 6P15P (SV83) the EL83-PL83/EL84 mode DPDT switch is in EL84 mode = pins 1 & 9 not tied. EL83/PL83 mode ties 1 & 9.
Doug,
Thanks for those measurements. They constitute a valuable data point, and I will make note of it in study. Thank you. Please let us know your results when you measure power output.
Given the screen rating max of 200V claimed for the SV83 your results with the PL83 are noteworthy*. At you operating point I estimate that your PL83 screens are dissipating around 1.1 watt, which is well within the dissipation max of 2 watts for the PL83 (and 1.75 w for SV83). The plates are dissipating ~9.5 watt, a little over specs (9watt) so you may want to keep an eye on that. As noted above, with 12 watts the SV83/6P15P would be loafing under these conditions.
*My theory is that Svetlana arbitrarily gave a screen rating of 200V for the SV83 for marketing purposes and to distinguish it from EL84. As many had stated before, the important specification is the dissipation rating - make sure you are below dissipation limits while you exceed the screen voltage rating.
Pleasure, no problem.
The 10 6P15P valves (I paid £10 for 10 so can't complain) are proving to be a bit more work getting them matched (for me, matched for guitar use is within 25%)
I found a pair that are 1.49v and 1.4v drop CT to anode so almost good enough for 'hifi'.
Bias is -10v
Anode current 27.6mA and 32.4mA
Screen resistor (468Ω) v drop is 2 and 2.5 = 3.5mA and 4.4mA
Maybe add some -ve bias to cool em down.
FYI, I have the Thomann Germany (Made in China) version of the Monoprice 15 watter, it has a pair of 6P14P rebranded TAD EL84-R.
Doug