# Rebuild or Trash it??

#### Dr.killjoy

Joined Apr 28, 2013
1,196
I had to sell my nice digital scope to pay bills but I still have my bk 20mhz analog scope..It needs alot of work and I have been working on it lately. Before I had a blanking problem and now it's got all kind problems .. I tried putting it back together after new bnc and switch 2 connectors that got mixed up ans turned and gave me no image on the crt.. No black smoke or charing but now I get all kind of funky dots on the crt.. Right now I am so frustrated with this scope that I am ready to throw it in the trash..
Do you guys think I should repair it and is there anyone to help if I got questions ???

Oh its a
BK Precision Model 2120 20mhz

#### Lestraveled

Joined May 19, 2014
1,946
Do you have the schematics for it?

#### dl324

Joined Mar 30, 2015
15,511
If it were me, I'd try to fix it because anything is better than nothing. I would have fixed it before I sold the DSO...

#### Dodgydave

Joined Jun 22, 2012
10,684
You need a scope to fix a scope, can you get the circuit diagram, if not its hard work.

#### Dr.killjoy

Joined Apr 28, 2013
1,196
I have full schematic,owner's manual,and service manual. I would have love to use my dso before I sold it .. But my plan was to donate the analog scope and use the dso but needed money last minute to pay rent.. So I am trying to figure out the problem and will post pics of the screen in a little bit when I get time..

#### dl324

Joined Mar 30, 2015
15,511

As @Dodgydave pointed out, unfortunately you usually need a scope to fix a scope.

#### Dr.killjoy

Joined Apr 28, 2013
1,196

As @Dodgydave pointed out, unfortunately you usually need a scope to fix a scope.
What should be the course of action then ??

#### dl324

Joined Mar 30, 2015
15,511
What should be the course of action then ??
You might be lucky and get it working well enough without a scope.

Post pictures of what you're seeing. Do you have a signal generator?

#### Dr.killjoy

Joined Apr 28, 2013
1,196
You might be lucky and get it working well enough without a scope.

Post pictures of what you're seeing. Do you have a signal generator?
I don't have a professional signal generator but I do have diy pic signal generator that need to be finished soldered,does that help??

#### dl324

Joined Mar 30, 2015
15,511
I don't have a professional signal generator but I do have diy pic signal generator that need to be finished soldered,does that help??
I glanced through the calibration procedure and saw references to a 1MHz and 1KHz square wave.

For basic testing, you might be able to use the calibrator on the scope. It's around 1KHz and 0.2V.

The scope is old school with no custom IC's. 741's, a 308, one or two other opamps from the 70's, and a bunch of discretes.

#### Dr.killjoy

Joined Apr 28, 2013
1,196
Update time
Right now I am snow in and am not going any where for a while (See Pic below)..
But I have a little busy with work and trying to fix the scope ..
Last time I guess I missed something but the scope is up and running .. The scope though is very jittery and can change wave form just by messing with knobs or such .. Also the brightness changes with certain knobs and I am loosing my mind trying to fix this .... I got signals from both channels for calibration of the probes but the I am still getting extra feedback in the background.

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#### strantor

Joined Oct 3, 2010
6,383
Something loose in the CRT?
In my experience when something changes just by you farting within 5ft of it, it's a loose connection or a loose something-or-other. Since the problems manifest in the CRT i would start there. Doesn't have to be a loose wire, could be a loose magnet or ring, or whatever is inside a CRT, I'm not well initiated. I'm sure one our old school guys could be more specific.

#### dl324

Joined Mar 30, 2015
15,511
The scope though is very jittery
In what way? Pictures would be helpful.
can change wave form just by messing with knobs or such. Also the brightness changes with certain knobs
Which knobs? How does the waveform change?

#### gootee

Joined Apr 24, 2007
447
Update time
Right now I am snow in and am not going any where for a while (See Pic below)..
But I have a little busy with work and trying to fix the scope ..
Last time I guess I missed something but the scope is up and running .. The scope though is very jittery and can change wave form just by messing with knobs or such .. Also the brightness changes with certain knobs and I am loosing my mind trying to fix this .... I got signals from both channels for calibration of the probes but the I am still getting extra feedback in the background.
Usually, first check that the power rail voltages are all within specs. If not, and nothing obvious presents itself, change out any old electrolytic caps in the power supply (or check their ESR, Equivalent Series Resistance, first, to see if it's gone high). When the power supply output voltages are all within specs, try for the easy fix, by cleaning all of the pots, switches, connectors, pins, and contacts. Caig's De-Oxit products can work wonders. See caig.com. I have "fixed" many older scopes using only De-Oxit.

#### Dr.killjoy

Joined Apr 28, 2013
1,196
Something loose in the CRT?
In my experience when something changes just by you farting within 5ft of it, it's a loose connection or a loose something-or-other. Since the problems manifest in the CRT i would start there. Doesn't have to be a loose wire, could be a loose magnet or ring, or whatever is inside a CRT, I'm not well initiated. I'm sure one our old school guys could be more specific.
Yeah I am not sure either but I can't decide whither to trash it and buy 100mhz Tek with my tax money and lose the headache ..

In what way? Pictures would be helpful.
Which knobs? How does the waveform change?
It was the X-pos knob changes the brightness and will post pic in a little while..
Usually, first check that the power rail voltages are all within specs. If not, and nothing obvious presents itself, change out any old electrolytic caps in the power supply (or check their ESR, Equivalent Series Resistance, first, to see if it's gone high). When the power supply output voltages are all within specs, try for the easy fix, by cleaning all of the pots, switches, connectors, pins, and contacts. Caig's De-Oxit products can work wonders. See caig.com. I have "fixed" many older scopes using only De-Oxit.
I check all the rails and they are spot on and go through all that work seems a waste for this scope in my opinion..

#### Dr.killjoy

Joined Apr 28, 2013
1,196
Well I got a awesome deal on a TEKTRONIX 2215 60MHz oscilloscope ..It needs some works but I can't wait to play with my new to me scope ... Are there anything I should be worried about and are the manual and service manual easy to get ??

#### dl324

Joined Mar 30, 2015
15,511

#### Dr.killjoy

Joined Apr 28, 2013
1,196
Sorry everyone for changing up the game here but I placed a bid for $10+$14 shipped on a Tek 2215 scope and was not thinking ..But I got a surprise when he accepted the offer.. So I will have to see what happens and the scope looks pretty nice and it has a couple issues but will see if it arrives..I might keep working on the bk or donate it to someone local in NJ but will have to see how both scopes make out first..

The listing
FOR PARTS ONLY:
You are purchasing a TEKTRONIX 2215 60MHz oscilloscope. Power on test only. Unit power on and display comes on.Item has some scratches on it from normal wear also the handle will not lock into place because theres a few plastic knobs broke off or bent. All buttons and knobs seem to be in working order beside the power button is stuck on.

I would love to know how he is going to come out ahead here with shipping through Fedex ??
Shipping: This unit will ship via Fedex Ground within 1-3 business days of confirmed payment. We are able to provide tracking numbers upon request. Please be aware that as this item is being shipped through Fedex

Thank you very much for the manuals ..

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