Author Topic: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.  (Read 14040 times)

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Offline The GuyTopic starter

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Re: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.
« Reply #75 on: September 23, 2017, 07:52:20 pm »
ohhh got it....  the volts/div mechanism.... How do i take it out?
 

Offline Armadillo

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Re: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.
« Reply #76 on: September 23, 2017, 07:53:03 pm »
ok... replaced them parts and nothing happened. I went ahead and replaced the whole attenuator board with one from another scope and though the traces were completely out of the screen I could actually move channel 1 trace with the vertical position knob with the beam find button pressed. Then  put back the original board because I still want to repair it.

Voltages are the same.
 

Offline Armadillo

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Re: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.
« Reply #77 on: September 23, 2017, 07:57:49 pm »
Please don't mix match.. otherwise troubleshooting become exponentially bizarre !   hahaha ha LOL  :-DD
 

Offline The GuyTopic starter

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Re: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.
« Reply #78 on: September 23, 2017, 07:59:06 pm »
ok... replaced them parts and nothing happened. I went ahead and replaced the whole attenuator board with one from another scope and though the traces were completely out of the screen I could actually move channel 1 trace with the vertical position knob with the beam find button pressed. Then  put back the original board because I still want to repair it.

Voltages are the same.

Yeah... but what i did there is actually to replace the whole board... the whole circuit board. the whole thing ;) but only for a brief moment to see what happened.
 

Offline Armadillo

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Re: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.
« Reply #79 on: September 23, 2017, 08:29:05 pm »
The voltage at the JFET is not right.

For capacitors from 1000uf to 1nf and no leak? You mean the oil evaporated away? unlikely LOL.
So either leak onto PCB, Ghost hunt or attenuator problem.
 

Offline The GuyTopic starter

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Re: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.
« Reply #80 on: September 23, 2017, 08:33:26 pm »
The voltage at the JFET is not right.

For capacitors from 1000uf to 1nf and no leak? You mean the oil evaporated away? unlikely LOL.
So either leak onto PCB, Ghost hunt or attenuator problem.

If  I put ch1 in DC mode and measure dc voltage at the probe input I get 2.4VDC not so in ch2 But that´s probably coming from pin7 in Q13...
 

Offline The GuyTopic starter

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Re: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.
« Reply #81 on: September 23, 2017, 08:36:16 pm »
I doubt its the caps because I changed them for the ones from a working unit....
 

Offline Armadillo

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Re: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.
« Reply #82 on: September 23, 2017, 08:36:28 pm »
The voltage at the JFET is not right.

For capacitors from 1000uf to 1nf and no leak? You mean the oil evaporated away? unlikely LOL.
So either leak onto PCB, Ghost hunt or attenuator problem.

If  I put ch1 in DC mode and measure dc voltage at the probe input I get 2.4VDC not so in ch2 But that´s probably coming from pin7 in Q13...

Could be possible, then change new nfet for Q13A.    ;D
 

Offline Armadillo

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Re: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.
« Reply #83 on: September 23, 2017, 08:39:58 pm »
I doubt its the caps because I changed them for the ones from a working unit....

At least you should have measured the capacitance and ESR before plugging it in?
 

Offline The GuyTopic starter

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Re: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.
« Reply #84 on: September 23, 2017, 08:46:42 pm »
I doubt its the caps because I changed them for the ones from a working unit....

At least you should have measured the capacitance and ESR before plugging it in?

I dont know how to measure ESR... I just started a year ago building guitar amplifiers, and when I started I didn´t knew the difference of positive voltage and negative (not kidding), so this is rocket science to me Lol
 

Offline The GuyTopic starter

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Re: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.
« Reply #85 on: September 23, 2017, 08:47:46 pm »
Screw it, I´m gonna change that Q13 and see what happens.
 

Offline tautech

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Re: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.
« Reply #86 on: September 23, 2017, 08:52:45 pm »
I doubt its the caps because I changed them for the ones from a working unit....

At least you should have measured the capacitance and ESR before plugging it in?

I dont know how to measure ESR... I just started a year ago building guitar amplifiers, and when I started I didn´t knew the difference of positive voltage and negative (not kidding), so this is rocket science to me Lol
Measure, check, verify or you'll end up just chasing your tail.
Methodical processes need be employed....
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Offline Armadillo

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Re: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.
« Reply #87 on: September 23, 2017, 08:57:16 pm »
I doubt its the caps because I changed them for the ones from a working unit....

At least you should have measured the capacitance and ESR before plugging it in?

I dont know how to measure ESR... I just started a year ago building guitar amplifiers, and when I started I didn´t knew the difference of positive voltage and negative (not kidding), so this is rocket science to me Lol

You got good soldering and desoldering skills I would say..... I think you are pretty good at electronics .. at the very least you have the courage to hands-on...
 

Offline The GuyTopic starter

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Re: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.
« Reply #88 on: September 23, 2017, 09:07:42 pm »
I doubt its the caps because I changed them for the ones from a working unit....

At least you should have measured the capacitance and ESR before plugging it in?

I dont know how to measure ESR... I just started a year ago building guitar amplifiers, and when I started I didn´t knew the difference of positive voltage and negative (not kidding), so this is rocket science to me Lol

You got good soldering and desoldering skills I would say..... I think you are pretty good at electronics .. at the very least you have the courage to hands-on...

I`m a high end jeweller by day and amp builder by night... I know how to work with tiny stuff  ;)

Damn... how do I desolder the fet.... that`s a hard one
 

Offline The GuyTopic starter

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Re: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.
« Reply #89 on: September 23, 2017, 09:52:33 pm »
Yep.... it is the fet. Took it out, tested it and there is conductance between pin 7 and pin six... it should read open.
 

Offline The GuyTopic starter

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Re: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.
« Reply #90 on: September 23, 2017, 10:20:42 pm »
IT Wooooooooooooooooooooooooooooorksssssssssssssssss!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!  :box:

Yeeeehaaaaw!
 

Offline The GuyTopic starter

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Re: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.
« Reply #91 on: September 24, 2017, 12:26:19 am »
Thanks Armadillo! You`ve been most helpful  :clap:

I hope to have the opportunity to give you a hand as well someday.

Now I need to calibrate this thing because it`s a mess. Volts x10 in channel 1 is completely out of whack.

Hopefully there won`t be no more surprises.

 :-+
 

Offline Armadillo

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Re: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.
« Reply #92 on: September 24, 2017, 12:36:13 am »
Congratulation!................................................................................................
You did it..

 :scared: :clap: :phew: :box: :-DD
 

Offline The GuyTopic starter

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Re: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.
« Reply #93 on: September 25, 2017, 03:39:25 am »
Congratulation!................................................................................................
You did it..

 :scared: :clap: :phew: :box: :-DD

Yeah man... we did it!! I already calibrated it (well, almost. Need a time mark generator) and it works like a charm.

https://youtu.be/vE4YOKN6nac
 

Offline tautech

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Re: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.
« Reply #94 on: September 25, 2017, 03:58:40 am »
Mr Dean and Ben next.
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Offline The GuyTopic starter

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Re: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.
« Reply #95 on: September 25, 2017, 04:16:12 am »
Mr Dean and Ben next.

Yessir! Tomorrow I start bringing Mr. Dean back to life! ...screwed up power supply I guess.

 :-BROKE
« Last Edit: September 25, 2017, 05:09:08 pm by The Guy »
 

Offline Armadillo

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Re: Problems with my scope (Charlie) Tektronix 2225 vertical amplifier.
« Reply #96 on: September 25, 2017, 04:19:16 am »
Looks like new. Great Job!  :-+  :scared: :clap: :-/O
 


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