... So, I put in place of 33K of anode RO2 a 5K resistance ... here are the voltages detected ....
... Yes, maybe too low 5K, can create problems. The input voltage is reduced to 130V. But if I put a 200-0-200 transformer, instead of the one supplied by 160-0-160 ..... do you think can help?
Mmm, maybe it is normal, probably some filtering after tuberectifier that reduced voltage in original state already like 40V, now 70V. AC160-DC225-tuberectifier-25Vdc=DC200V, 160 measured, so 40V originally dropped in some way at the current asked then. Resistor(s) between tuberectifier and schematic showed. Could be normal after all.
Yes that looks like 100R-330uF followed by 10k-330uF and then RO1 and RO2 plate resistors. But I can't see connections/tracks, you probably can. If connected like that the 10k is reason for voltage drop and does entirely explain voltage drop you measured, no other problems needed imo.
RO1 operating point looks awfully low with the 82k/2.2k and measured values don't match tubecharacteristics probably because set entirely at the bottom, uncertain area. Changing 82k for 33k should make RO1 behave a little more predictably.
Later you can set voltage to higher value by changing powersupply filters, lowering the 10k resistor. But preamp should work with lower voltages.
RO1 operating point looks awfully low with the 82k/2.2k and measured values don't match tubecharacteristics probably because set entirely at the bottom, uncertain area. Changing 82k for 33k should make RO1 behave a little more predictably.
Later you can set voltage to higher value by changing powersupply filters, lowering the 10k resistor. But preamp should work with lower voltages.
Hi all.
I was given an original Hengpen-13 and I was looking for opinions before turning it on for the first time.
This 3D was very helpful, I even found the schematic.
I have to say I don't like it very much indeed... (too much gain and too much fb and too much Zout?), but I still have to heard it.
Below my potential mods about it:
I was given an original Hengpen-13 and I was looking for opinions before turning it on for the first time.
This 3D was very helpful, I even found the schematic.
I have to say I don't like it very much indeed... (too much gain and too much fb and too much Zout?), but I still have to heard it.
Below my potential mods about it:
Attachments
Using an LED to bias a cathode follower is a very bad idea. It is literally the opposite of what is required.
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