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Checkout problem TSE.

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Hello,
The final checkout according Checkout | Tubelab doesn't mention any B+ or B- values wich should be measured at the different stages (with or without tubes).
My understanding of schematics is very limited so these values would be a big help in the checkout procedure.
My configuration is:
300b version (shungang)
transcendar opt 5K
5ar4 rectifier
4852 tungsol
a custom power transformer image attached
The sockets are raised of the board by 6cm with copper rods.

I did have a problem with the final checkout of my tse. The first item i encounterded was that c3 cooked within a few seconds of powerup. After replacement with a 4700uF 16v (4700uF 6.3V electrolytic capacitor) one the specified check worked fine until i checked the filament supply it measured over pin 1 and 4 11 volts, the specs for 300b it should be around 5v.
B+ without tubes is -00 without tubes and 430v with rectifier.
The bias of the 4853's is about 175v.
I hope someone can give me a hint where to look.

Greetings Mark
 

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The TSE is more of an intermediate level project, so the instructions are a bit less detailed. George's "Tubes and Applications" page gives an idea what to expect for B+ voltages.

Tubes and Applications | Tubelab

With no load, that B+ sounds reasonable. You also have the 5842s setup correctly, so that is a good sign. Your filament voltage is way too high, obviously. It seems like you have an error in that part of the circuit. Perhaps there is a short or U1 is fried. Can you measure the voltages across C1, C3, and R1? Also check you bias voltage while you are at it (45 tube pin 3 to ground).
 
Hi,
I took some additional measurements this morning:
All with rectifier and pre-tubes in place.
B+ 408
B- -247

300b tube pin 1-4 filament supply 15,5 volt
Tube pins to ground
1 filament + = 15,4v
2 Plate = 26,1 & 33v
3 Grid = 415 (positive?)
4 filament neg= 0

Across C1= 15,7v
Across C3 = 15,02v.
Across R1 = 0 removed from pcb and resistance measures ~ going to replace it.
I hope this will do the trick and the filament supply will return to normal.
 
Do not install the 300B's until you get this fixed.

15.5 volts is way above the maximum spec for the filament regulator. The chip is probably blown.

The filament winding on your power transformer is 12.6 VCT volts which is too much. You need a 6.3 VCT transformer. Since you are using 300B tubes you should be able to use half of the winding for 6.3 volts. Connect the center tap to T1-7 and one of the 6.3 volt terminals to T1-8. Make no connection to T1-6 or the other 6.3 volt terminal on the transformer. The voltage across C1 should now be around 7 volts. If the voltage on C3 is not 5 volts your regulator chip is probably dead.

Do not install the 300B's until you get this fixed.
 
Hi. I did as instructed and i have 7.5v over c3. So i will need a new voltage regulator. Has anyone a source for sharp PQ5EV5 in europe. With mouser or digikey i have to pay $18.00 shipping and here 21 % tax over the total invoice. Ridiculous.a set 300b from china just $60.
Already many thanks.
 
Replaced the resistors r1/r2/r35 . Now i have 5volt at the filament.

Next step in the checkout, another problem. At the 5842's i have B+ on the plate/gnd (pin 9) , that is when i use both tubes, with just one 5842 i get eventually at the target 175v. first it surges to 440v in about 10 seconds then drops in another 30 seconds to around 175v. Both channels and tubes same behavior. Checked r16 and r17 seems oke. So I thought they went in temperature shutdown so I placed a bigger heatsink on the mosfets (2SK3564) no change. they are very hot to the touch (two seconds before I need to pull my finger away). tried with a small fan still no change.
I am still in the breadboard stage, star grounded to outlet(do I need to ground the pwt and choke housing in this stage?)

My b+ is at 417v without the 300b's.
I welcome some suggestions.
 
Last edited:
My measurements:
no tubes:
B+ -0 v
B- -292v
filament 4.97v

with rectifier:
B+ 430v
B- 292v
filament 4.97v
grid -143v

rectifier+5842
B+ 425v
B- -288v
5842 plate to gnd left 248v
5842 plate to gnd right 237v
(is adjustable but only up)
voltage across r16/r27 = 3.21v
voltage across r17/r28 = 0v
 
I have the tse working. The problem was with the 5842`s.
Replaced them and now sound is excellent. Even on my 85dB OB full range. .
I do have a little problem.after about 10 minutes of use the power drops. It looks like a temperature fail safe. tried it with a little pc fan on the mosfets but not much, if any, difference.
I don't have any silver paste at hand, is that much difference anyhow?
Still in breadboard state but these are my measurements with al the tubes mounted.
B+ = 394volt
300b filament 4.96volt
5842 = 175volt
bias 64 ma

any suggestions would be much appreciated.
 
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