Reel to reel valved tape recorder Geloso G258, problem

[Lef de art]

Hello again guys.
I have changed the electrolitic and papper capacitors and the problem is resolved. The recording and erase process now works normally.

But i have noticed that when i power on the system, the middle lamp 12AX7 , lights really much for 1/2 seconds , then decrease and remain in the normal light as the other lamps .


I believe it is over voltage in first 2 seconds because of some capacitor.
Any idea ?

This happens only when the system is off for at least 30 minutes.

I don't know if this happens and in the other 12Ax7 lamp because it is protected by a pocket all around and i can't see her base.
For sure does not happen to the 6AQ5 or to EM84

[Lef de art]

I have checked the other lamps and does not happen to the other 12AX7 , 6AQ5 or to EM84 lamp.

Only to the one 12AX7 in the center

[Techman]

Just a slightly dodgy valve, I wouldn't worry about it. Some of those valves do that normally anyway.

[Lef de art]

Thanks Techman. You are my hero.

And one last advice please.
I have changed the selenium rectifiers. .
i have replaced them with 4 silicone diodes.
The problem here is that the selenium rectifiers drop some volts and the silicon diodes dose not do this.

The input ac volt in selenium is 240 volts . After selenium the dc is 210.

With the silicon diodes the ac voltage is 240 and the dc is still 240.
I have ad one 200 ohms 6 Watts resistor in the output but the voltage is still 240.
What i do wrong here ?

[Techman]

Yes, but what's the DC reading on either side of your series resistor? We need both readings here, forget the AC reading before the new rectifier bridge.

[Lef de art]

I think I don't understand what to measure

Before with selenium it was
AC 240 and the output DC 210 .

Now with silicone diodes is

AC 240 and output DC 240. ( With no resistor)

After i have ad 200 ohms, 5W resistor in the anode i still have
AC 240 and output DC 240

[Techman]

Hello,

This must be due to having no load on it.

With the rectifier and series resistor supplying HT to the tape recorder circuitry, there must be a difference in voltage - ie, with a current being drawn through the 200 ohm resistor there must be a voltage drop across it, so the voltage must be lower on the output side of the resistor than the input side, but it won't be if there's no load connected to it.

[Lef de art]

I see.
Now i understood the way it works.
I will make the measurements and i will ad any resistor if it needs.

I want to thank you all for your help.
By all this process, and by your help , the tape recorder works again and my skills have improved really much.
A long process but at the same time very beautiful.
As for the filing when i look at it now, working , is undescribable.

Really thanks to all of you guys..
Special thanks to Techman for his time to share with me his skills.

[Lef de art]

Hello forum.
One question for anybody how may knows.
After i have changed all caps and 2 resistors close to the EM84 tube the indications on the tube is all the time in the half. Before it was in the start position. Now it stays in the middle with no reason.
Any ideas ?

I have uploaded 2 pictures with the before and the after situation.