Help for TubeHead DC rectifier
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Author:  furthergraphics [ Thu Nov 05, 2015 3:59 am ]
Post subject:  Help for TubeHead DC rectifier

I built a Tube Head with the 9305b pc board.
The problem is the rectifier. doesn't work correct.
Measurements are:
D1: +12,5V
D2: -16,5V

R1: 6V- left side to ic direction

IC2 and IC3: Pin 4: -14,7V
Pin 8. +6V
IC1 Pin : 12,6V
IC1 Pin 2 4 and 6 is: +6V

I have checked solder work and have changed c1 to c4, also changed the D1 and D2. No results.

Please help. Any Suggestions? :cry:
Regards: Peter

Author:  PAiA-Scott [ Thu Nov 05, 2015 12:13 pm ]
Post subject:  Re: Help for TubeHead DC rectifier

The normal drop across the R1 and R3 DC Filter input resistors is about 2V. You are seeing about 6V on the positive voltage. Double-check to be sure they are both brown-black-brown coded 100ohms. Otherwise, there must be something that is putting extra load on the positive DC. Electrolytic capacitor polarity? Op-amp output seeing abnormal load?

Connecting the DC supply for the filament power might be the culprit. It was a solution for minimizing hum when we once stocked some tubes made in China, but with the Sovtek brand supplied in the kits, the modification is not necessary.

Author:  furthergraphics [ Thu Nov 05, 2015 1:20 pm ]
Post subject:  Re: Help for TubeHead DC rectifier

Hello Scott,

Sorry my English is not the best...
Its hard for me to ubderstand everything.
I took 100 Ohm resistor but the blue ones with 1% tolerance, also the others are 1%. I double-checked Electrolytic capacitor polarity.
As I wrote ic2 and ic3 have Pin 4: -14,7V
Pin 8. +6V, so i thought its less V Pin 8 also must have ca.15. as you wrote in the troubleshootings...
What do you mean: Op-amp output seeing abnormal load?

And what do you mean dc supply for the filaments. They get 12v ac.
and the 45 V arent working because of the less 6V i think or is that wrong?

Which modification is not necessary?
what can I do now?

thanks: Peter

Author:  PAiA-Scott [ Thu Nov 05, 2015 2:50 pm ]
Post subject:  Re: Help for TubeHead DC rectifier

The modification I mentioned is the last example posted here:

However, it is for the 9407 Tube MicPreAmp rather than 9305 TubeHead, and tapping DC from the negative supply, but it could have been a reason for the extra current flow if it had been in place (and on the positive supply).

If you have the 12VAC to the tube filaments as is normal, then please disregard my mention of DC supply to the filaments.

The voltage to pin 8 of the op-amps should be about the same as the voltage to pin 4 of the op-amps.

So, there must be more current flow on the positive side, resulting in less voltage.

The 4049 IC has the positive DC voltage to it, but not from the op-amp side of R1. Instead, it is from the D1 and C1 side and labeled Vcc. The voltage is more here and this is to get the most from the voltage multiplier circuit section including the 4049.

If this 4049 feels warm to hot when touching it, it might have failed (accidental short circuit???). If so, it could be using more of the positive DC supply power than is normal, resulting in lower than normal voltage o the op-amp side of R1.

If the 4049 is cool to the touch, then it is probably doing its job of switching voltage on and off to the following diode and capacitor voltage multiplying (x3) section. For the 12V to pin 1, the voltage switching will be 0 - 12 and DC measurements of C8, then C9, and then C10 should show 12V, 24V, and 32V (not the 45V on the schematic, but OK).

The 6V you report on the 4049 output pins 2, 4, and 6 make it likely the IC is operating and switching on/off at about 40KHz.

So, an abnormal load on the op-amp output might be post-audio oscillation occurring, or, a shorted shielded cable to an output connector with the internal wire touching the grounded shield wire.

This could occur from some trouble on the board or wiring such as soldering or other cause for a short- or open-circuit.

If you can email photos of the top and bottom sides of the board, and control/connector wiring I might be able to spot trouble and reply with advice.

And, thanks to:

Die Modifikation I erwähnt ist das letzte Beispiel hier gepostet:

Jedoch ist es für den Schlauch Mikrofon-Vorverstärker 9407 anstatt 9305 Röntgenstrahler und Klopfen DC von der negativen Versorgungs, aber es könnte ein Grund für die zusätzliche Stromfluss, wenn es an Ort und Stelle (und auf den positiven Versorgungs) gewesen.

Wenn Sie die 12VAC zur Rohr Filamente als normal ist, dann ignorieren Sie bitte meine Erwähnung von Gleichstromversorgung zu den Filamenten.

Die Spannung an Pin 8 der Op-Amps sollten etwa die gleiche wie die Spannung an Pin 4 der Operationsverstärker sein.

So muss es mehr Stromfluss auf der positiven Seite zu sein, was zu einer geringeren Spannung.

4049 IC hat die positive Gleichspannung an, aber nicht von dem op-amp Seite R1. Vielmehr ist es aus der D1 und C1 Seite und markiertem Vcc. Die Spannung ist hier mehr, und das ist, um das Beste aus der Spannungsvervielfacherschaltung Schnitt einschließlich der 4049 zu bekommen.

Wenn dies 4049 fühlt sich warm bis heiß, wenn es zu berühren, könnte es versäumt haben (versehentlichen Kurzschluss ???). Wenn ja, könnte es sein, mit mehr von der positiven Gleichstromversorgungsleistung als normal, was niedriger als normal Spannung o des Operationsverstärkers Seite R1.

Wenn die 4049 ist kühl anfühlt, dann ist es wahrscheinlich, seine Aufgabe der Schaltspannung ein und aus, um folgenden Abschnitt Diode und Kondensatorspannung Multiplikations (x3). 12 und DC-Messungen von C8, dann C9, C10 und dann sollte zeigen, 12V, 24V und 32V (nicht die 45V auf der schematischen, aber OK) - Für die 12 V an Pin 1 wird die Spannungsschalt 0 sein.

Die 6V Sie auf den 4049 Ausgangs-Pins 2, 4 zu melden, und 6 machen es wahrscheinlich, das IC in Betrieb und Ein- / Ausschalten bei etwa 40 kHz.

So, eine anormale Belastung auf den Operationsverstärker-Ausgang könnte post-Audioschwingungs auftritt, oder ein Kurzschluss abgeschirmten Kabels an einem Ausgangsanschluss mit dem inneren Draht Berühren des geerdeten Schirmdraht.

Dies könnte einige Schwierigkeiten auf der Platine oder Verdrahtungs auftreten, wie Löten oder andere Ursache für einen Kurz- oder Leerlauf.

Wenn Sie sich die Fotos von der Ober- und Unterseite der Platine, und die Steuerung / Steckerverdrahtung eine E-Mail, ich könnte Probleme erkennen und antworten mit Beratung.

Author:  furthergraphics [ Thu Nov 05, 2015 4:33 pm ]
Post subject:  Re: Help for TubeHead DC rectifier

Hello Scott,

Thank you now Im a little bit more clever how the TubeHead works.

I send you the pictures of mine as you ask for.
I cant detect something wrong. I have taken stereopots instead of monos.

Hope you can see something. I sent it to your emailaccount.


Author:  furthergraphics [ Thu Nov 05, 2015 4:48 pm ]
Post subject:  Re: Help for TubeHead DC rectifier

I forgot,
the ic 1 gets lightly warm. stays not cool.
thanks Peter

Author:  furthergraphics [ Tue Nov 10, 2015 7:32 am ]
Post subject:  Re: Help for TubeHead DC rectifier

Hello Scott,
oh my God . i overlooked a terrible fault with this solderbridge...

After resoldering the otherbad connections. I can measure on pin 8 and 4 from the dual op amps the -14 and +14 Volts . Fine.
Also I resoldered the ic1-base and now its multiplying fine from 16 to 50V .
also on R6 and R43 I have the 50V.

Is that ok or is 50V to much for the tubes?
The IC1 is getting more warm to near hot.

Insame Im happy. now. " Two eyes are seeing more than one....
Thank you very much.


Author:  PAiA-Scott [ Tue Nov 10, 2015 11:54 am ]
Post subject:  Re: Help for TubeHead DC rectifier

Hello Peter.

Good! The voltages you report are good too. IC1 might be getting voltage near its normal limit of 18V, causing it to run warm-hot. This is OK. They can operate up to 22V, possibly even higher. The DC power supplies on the board are unregulated, so the more the AC voltage from the transformer, the more the DC and the less, the less. The voltage of a kit and its transformer will vary as the mA or A rating of the transformer is more or less than the 300mA specified for the kit.

Thank you.

Author:  furthergraphics [ Sun Nov 15, 2015 5:58 am ]
Post subject:  Re: Help for TubeHead DC rectifier

Hello Scott,

So here I'm once again...
I put the whole circuit with all in my woodencase .

Results: I can hear a hum in my loudspeakers. Not terrible loud so I could leave it on for first tests.
Music is contollable with the pots. Output is with most hum in the first part of the adjustable way.(but never goes away) Drive and Blend works, also the clipping Led.
But sound is without highs and middle, terrible muddled and big boomy-bass and the hum is loud,not normal sounds like malfunction.

Is it possible that the tubes have a malfunction? :?:

Here are the measurements:
IC1 works. all ok.
IC2: pin 8: +13v pin 4 -14v
pin 1: 0,01v
pin 7: 0,05v
IC3: pin 8: +13v pin 4: -14v
pin 1: 0,01v
pin 7: 0,05v
IC4: pin8: +13v pin 4: -14v
pin1: +12,5v
pin7: +12,5v
R6: +46v
R34: +46v

R10: +46v
R38: +46v
When the tubehead is on I can measure with the tubes inserted
on tubepin 1: 28v, on tubepin 6: 28v.
without the tubes I can measure on both pins 1 and 6: 42v.
is that normal?
Do i need the connection on the blend pot between lug 2 and 2 or can i neglect it, because its a stereopot?
All summarized Scott: What can i do to make my tubehead run ? :roll:

thanks: Peter

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