[Boatanchors] Fw: TV-7/U restoration help

[Luca Rossi]

Good news:

I have found one of my TV-7/U problems: a broken wire between R113 and R115.

Now all the resistance values on E106 are correct and the instrument pass
the simulated tube test (para. #26 TM11-6625-274-35, 40 scale divisions for
positions B, D, E of Function Switch and 20 scale division for the C
position).

Unfortunately, the meter indication trouble about the plate voltage test and
the screen grid test still remain, even if it has changed:

Para#23, plate voltage test: meter indication trouble. I can read the
correct voltage (147V between pin 3-6, with a 379.00kohm resistor) when I
depress button 3 (Mut.Cond.), but the meter needle doesn't move from 0 (all
positions of Funcion Switch).

Para#24, screen grid voltage test: meter indication trouble. I can read the
correct voltage (128V between pin 4-6, with a 379.00kohm resistor) when I
depress button 3 (Mut.Cond.), but the meter needle doesn't move from 0 (all
positions of Funcion Switch).
And I can read the correct voltage (57V between pin 4-6, with a 379.00kohm
resistor) when I depress button 3 (Mut.Cond.) and 2 (Diode), but the meter
needle doesn't move 0 (all positions of Funcion Switch).

I don't reach to undestrand where is the problem!

Regards,
Luca.

----- Original Message -----
From: "Luca Rossi" <chopin.i at inwind.it>
To: <boatanchors at mailman.qth.net>
Sent: Thursday, April 20, 2006 2:55 PM
Subject: TV-7/U restoration help


> Hello.
>
> I am writing from Italy, about the restoration af my first TV7 tube
tester.
>
> I have had it from a friend, due to the missing resistors holder E106 and
> rheostat R126: this friend doesn't have the time to find the spare
> components and to rebuild the circuit.
>
> Currently I have rebuild the E106, replaced the CR101 with 2x 1N4148, the
> 5Y3GT with a nos 5Y3WGTA, the 83 rectifier with a solid state type and all
> the carbon resistors. Now I am trying to calibrate this TV7, but I am
> experiencing some troubles.
>
> The steps I have followed:
>
> Referring to the TM11-6625-274-35 page 9:
> the line voltage test circuit is OK: depressing the Line Adj button, the
> Line Test segment is matched by the meter when a 121Vac is between
terminals
> 19 and 37 of the power transformer.
>
> Referring to the TM11-6625-274-35 page 39 and over, TV-7 settings HS
53460,
> bias=0, shunt=0, Function Switch=B:
> Para#22, bias voltage test: PASSED
>
> Para#23, plate voltage test: meter indication trouble. I can read the
> correct voltage (151V between pin 3-6, with a 379.00kohm resistor) when I
> depress button 3 (Mut.Cond.), but the meter needle doesn't moove upon 35
> scale divisions.
>
> Para#24, screen grid voltage test: meter indication trouble. I can read
the
> correct voltage (128V between pin 4-6, with a 379.00kohm resistor) when I
> depress button 3 (Mut.Cond.), but the meter needle doesn't moove (when the
> Function Switch is on B, but if I set the Function Switch to D or E, it
> point the ~48th scale division).
> And I can read the correct voltage (55V between pin 4-6, with a 379.00kohm
> resistor) when I depress button 3 (Mut.Cond.) and 2 (Diode), but the meter
> needle doesn't moove (when the Function Switch is on B, but if I set the
> Function Switch to D or E, it point the ~21st scale division).
>
> Para#26, simulated tube test: meter indication trouble. The needle doesn't
> indicates 40 scale divisions: it run to the right of the dial.
>
> Furthermore, I have checked the voltages and resistances on the E106 as
> shown into the figure 33 of TM11-6625-274-35:
> all seems to be ok, only the resistance on the pins of R119 are different
> from the TM: 850ohm instead of 155 and 2,3k instead of 1,9k.
> The resistance between terminal #19 of the power transformer and
> R123-R124-R125 is near to 5Mohm but I think it would be due the new CR101.
>
> Any idea??
>
> Many thanks and regards,
> Luca.
>
>