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Old 10-19-2019, 04:33 PM   #1
Lef de art
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Default Reel to reel tube recorder Geloso G258, problem

Hello my friends.
I have bought recently a almost unused reel to reel tube recorder, Geloso G258 feom 1958
But because of his age it is time for changing his electrolytic capacitors.
I leave in Cyprus so it will be more easy for me to buy them on line because here i don't have many choices in electronic components.

The capacitors i need are the following.

*16μf 200ν-250v
*32μf 350v-500v
*25μf 30v
*150MF 15v
*0,0047μf 20%
*0,0022μf 25%

and one double/dual capacitor 25+25μf 200vcc-350v (if i write it correctly)

Please if you can help me will be a huge help.
Thanks in advance

Sorry for my bad English
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Old 10-19-2019, 06:36 PM   #2
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Default Re: Reel to reel tube recorder Geloso G258, problem

Axial electrolytic capacitors are hard to find. I don't know what parts are available in Cyprus.
I use radial capacitors and bend one lead over. A little bit of silicone caulk/glue to hold it down. Modern capacitors are so much smaller.

16μF 200V (250V surge) - use 16μF 250V
32μF 350V (500V surge) - use 33μF 450V (two needed)
25μF+25μF 200V dual (350V surge) - use two 22uF 250V

25μF 30V - use 33μF 50V
150μF 15V - use 220uF 16V or 25V.

0,0047μF ?V 20% - use 4n7 400V mylar film cap like Epcos B32529C6472
0,0022μF 630V 25% - use 2n2 400V mylar film cap like Epcos B32529C6222


Geloso G258 Schematic: https://www.eserviceinfo.com/downloa...loso_G258.html
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Old 10-19-2019, 08:02 PM   #3
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Default Re: Reel to reel tube recorder Geloso G258, problem

Really thanks Redwire.
I will try to find them here but really is difficult in Cyprus.
There is not any on line way to buy them ?
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Old 10-20-2019, 04:30 AM   #4
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Default Re: Reel to reel tube recorder Geloso G258, problem

The only 16μF 250V capacitors i can find are for starting motor use with no polarity .
Can i use no polarity capacitors ?
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Old 10-20-2019, 09:36 AM   #5
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Default Re: Reel to reel tube recorder Geloso G258, problem

I have ordered them, so just waiting to arrive
Thanks Redwire. Your help was really big.

One more question. I must change and this one.
Any idea with what type and what uf ?
Electrolytic one ? Bipolar or not ?
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Old 10-20-2019, 02:18 PM   #6
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Default Re: Reel to reel tube recorder Geloso G258, problem

You are over 5,000 miles around 9,300km away. I don't know electronics parts distributors over there. RS Components might be good but they like to sell bags of 5 or box of 1000.

The 0.1uF 400V cap connects to mains, so I would use a film cap 275VAC 0.1uF with X-cap safety rating. Look at Epcos B32653, Kemet R46 series.
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Old 10-20-2019, 03:06 PM   #7
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Default Re: Reel to reel tube recorder Geloso G258, problem

Quote:
Originally Posted by redwire View Post
You are over 5,000 miles around 9,300km away. I don't know electronics parts distributors over there. RS Components might be good but they like to sell bags of 5 or box of 1000.

The 0.1uF 400V cap connects to mains, so I would use a film cap 275VAC 0.1uF with X-cap safety rating. Look at Epcos B32653, Kemet R46 series.
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Old 10-22-2019, 09:59 PM   #8
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Default Re: Reel to reel tube recorder Geloso G258, problem

https://www.badcaps.net/forum/attach...3&d=1571582161
That is a snubber cap for the switch (it is connected in parallel with the AC switch contacts).
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Old 10-23-2019, 07:23 PM   #9
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Default Re: Reel to reel tube recorder Geloso G258, problem

Quote:
Originally Posted by budm View Post
https://www.badcaps.net/forum/attach...3&d=1571582161
That is a snubber cap for the switch (it is connected in parallel with the AC switch contacts).
Is a important capacitor for the system ?
It must be changed or does not really matters ?
It is a papper capacitor so for sure does not work correctly any more.
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Old 10-23-2019, 10:08 PM   #10
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Default Re: Reel to reel tube recorder Geloso G258, problem

It helps to reduce switch arcing, you should replace it since it is old paper based cap.
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Old 10-24-2019, 02:16 AM   #11
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Default Re: Reel to reel tube recorder Geloso G258, problem

Thanks Budm.
I have ordered them and i wait to receive them so i can start the replacing process.
It will take some time to receive them but i will update the forum with the process
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Old 11-01-2019, 07:13 AM   #12
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Default Re: Reel to reel tube recorder Geloso G258, problem

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 10 minutes.

This does not not happen to the other 12AX7 , 6AQ5 or to EM84 lamp.
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Last edited by Lef de art; 11-01-2019 at 08:07 AM..
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Old 11-03-2019, 06:39 PM   #13
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Default Re: Reel to reel tube recorder Geloso G258, problem

This is normal - when the tube is cold, high current surge for the heater and the fine wires will light up bright orange until the heater is warmed up.
Geloso put two 3.3R resistors for tube V1a heater but not the second 12AX7 for some reason. It might be for lower noise and hiss.
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Old 11-03-2019, 07:33 PM   #14
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Default Re: Reel to reel tube recorder Geloso G258, problem

Thanks Redwire .
It is the lamp. I have changed the position with the other 12AX7 and the phenomenon occurred in the same lamp but this time in the different positions.
As i understood is not something important. Does not mean the bulb is defective so everything is ok
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Old 11-06-2019, 02:22 PM   #15
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Default Re: Reel to reel tube recorder Geloso G258, problem

Comparing the sound i have now with the sound i had before changing the capacitors i have the filing that i have lost enough bass, low frequencys.
As it is normal in the replacement capacitors process it wasn't easy to find the exactly value in capacitors. So some changes was made...
There is any chance the following replacements to be wrong?
What is your opinion?

0,005uf / 150v replaced with 0.0056 250v

0,002uf / 400v replaced with 0,0033 400v

0,025uf / 300v replaced with 0,027/ 400v

0,5uf / 150v replaced with 0,56/ 250v


Or this differences are not important?
Thanks in advance guys
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Old 11-06-2019, 04:33 PM   #16
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Default Re: Reel to reel tube recorder Geloso G258, problem

If the coupling cap between audio stages has decreased value then you will lose low end frequency, but you put in higher value so it should not decrease the low frequency response. The Cathode bypass caps will also affect the low frequency response.
https://www.v-cap.com/coupling-capacitor-calculator.php

Last edited by budm; 11-06-2019 at 04:48 PM..
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Old 11-06-2019, 09:31 PM   #17
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Default Re: Reel to reel tube recorder Geloso G258, problem

I would say those differences do not matter, the capacitors are tiny bit bigger and would not make the bass go weak.
You must have mixed up a capacitor, or a new one is no good, or polarity backwards (for 25uF), or there is a wiring mistake putting in the new capacitor.

Check the capacitors, I think important (for bass) are:
25uF 30V cathode pin 2 EL95 electrolytic
20K 150V grid pin 7 12AX7 V1a
25K 350V plate pin 6 12AX7 V1a
10K 400V plate pin 1 12AX7 V1a / pin 2 12AX7
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Old 11-07-2019, 04:38 AM   #18
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Default Re: Reel to reel tube recorder Geloso G258, problem

Thanks Redwire. I will check them today.
The electrolitic capacitors work all good because i have changed them all in first stage and i then the recording quality was ok.

After i change all the papper capacitors the recording high frequencies are very weak.
And the recording sound has more treble.

But the changes are in recording .

Last edited by Lef de art; 11-07-2019 at 04:53 AM..
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Old 11-07-2019, 04:44 AM   #19
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Default Re: Reel to reel tube recorder Geloso G258, problem

The difference is on recording high frequencies .
The recording has lost high frequencies.

The playback mode with old capacitors recordings sounds ok.

Last edited by Lef de art; 11-07-2019 at 04:54 AM..
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Old 11-07-2019, 04:20 PM   #20
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Default Re: Reel to reel tube recorder Geloso G258, problem

Did you check/adjust recording bias? Tape heads are cleaned and de-magnetized?
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