No.111 - Tektronix 2215 Oscilloscope Repair
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- เผยแพร่เมื่อ 5 ก.ค. 2023
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This scope was kindly donated to the channel by Adam here in the UK. The report was that it was tripping RCD's and the display was distorted and stationary at the bottom left of the CRT.
Not particularly my main area of expertise and with multiple faults I gave it a go.
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Additional note regarding the transistor I swapped out. The BFR96S for the original BFR96:
BFR96 Ic = 75mA
BFR96S Ic = 100mA
The DC current gain (dB) is a little less on the S version, but I cal'd that out. I thought it better to have that slightly better Ic in the hope it makes it a little more robust.
You must use a matched pair, don't mix an S version with a non-S version as it unbalances the differential amp and one of the transistors will blow after a while.
What I would have given to be in with a chance of any kind of free scope when I was a young 'un, never mind a 60MHz Tektronix :-). Nice gesture, Ian - we need to encourage more youngsters into the field.
Not really me, it's thanks to Adam who donated it.
I would have sold my sister for a scope like this at a young age....:)
Very detailed explanation on troubleshooting and repair.
Thanks…..I try my best 👍
Even Tektronix used Rifas! Good idea to replace the IEC filter/socket. I had one of those go pop & let the stinky smoke out, in a Tektronix video signal generator.
Yes, those old Schaffner IEC-filters are prone to letting go........
Very good videos! Only criticism Warning High Voltage should be at beginning of every video when working on mains/ power supplies/valves etc, I worked over 40 years
on SMP, valves, HV business machines, p.a. Gear etc.! Yes I got bad shocks twice mostly stupid mistakes! i.e. examining motor field coils- I plugged in them instead of angle poise lamp and ended up against a door! Ouch!
Point taken.
Also the danger of charged capacitors or crt’s !
Nice. I have a 2213A which was my first oscilloscope :)
Had one at work in the 80's fixing arcade games.
Glad to see this one made it.
Exactly the right mix of details and progress; great repair video.
The vertical deflection problem looked just like what I had on a 2225, but in my case it was a fried resistor. The service manual said they switched from 5W to 7W during the production run and the 7W replacements I ordered were a good bit larger than the fried-looking one that died so I guess that explained that!
Yes, there's quite a bit of current being driven back and forth in that circuit. I had to change out both transistors at opposite ends to make sure the circuit was still biased and operated properly. It wasn't to start with and the good transistor was heating up!
Great repair and a good idea give it away to a youngster 🙂
Squeak !!!!!!!!!!!!!!!!!!!!!
Woof!!!
Great troubleshooting! Nice job.
Subscribed for the accent brother.
Great troubleshooting, enjoy to watch
Awesome ! I did a similar repair, few years ago, on a Philips CRT digital scope which is nice to have in your lab..
I have a 2215A that confounded my repair attempts over a year ago. A PSU fault remains after I fixed a few other things. I'll now go back and see whether your findings shed any new light, though the A version was a bit different. Thanks for taking us along with you.
Let us know how you get on with the 2215A.
Wow - memories. This was my first scope - well my employers! It was on my bench in the electronics dev lab at GEC Traction in Manchester - I want to say around 1982-3 ?
Mine (at work also) was a Iwatsu SS-5702 20MHz scope. It was there when I arrived 1984.
Nice repair Ian. I'm not so young anymore so I have no chance of winning the 'scope.
Whats the typical manufacturer spec on reading precision of those voltages in those analog oscilloscopes?
Enjoyed the video, Ian. I don't understand how RF transistors were used. Would like to have seen a picture of them in circuit. Thanks! John
Can only think that since those transistors are on the direct input path they will be subject to wide ranging input frequencies from DC to 60MHz, and to get as level a current gain versus bandwidth as possible they are using RF transistors. Just a guess though.
Nice video ! perfect for audio work would be very useful to me....... but A) I don't use twitter and .....B) I certainly can't get away as a young'un anymore not even in my dreams Lol ! very enjoyable as always....cheers.
What a fantastic job. I'd love to have that analogue scope. Do you know where I can get one of those trim tools, I've been looking for a while now but no luck?
Available on Ebay/Amazon "bourns trimming tool"
@@IanScottJohnston Thank you so much, just ordered one.
I have a tek 2225 analog scope and i know it has a very small amount of horizontal jitter as it can not be visible in normal operations.
But when i magnified the internal calibration scurewave to calculate rising time of that signal it can be visible. The isue is not quality of that signal because i have same problem when i want do same mesurement of signal rising time of my TDR circute. Intersting point is that this problem apear in first case i mean the internal calibration signal, just when slope switch of the scope in front panet set down . But in mesuring signal from TDR circuit acure eather the slope switch set up or down.
Could you gess the issue is in which part of circutry ? In trigger and slope circuit or in horizontal amplifire ?
TNKS
Ian: 👏👏👏👏👏👏👏👏👏👏👏👏👏👏👏👏👏👏
I have a 2214 that has a problem of, when you turn up the trace intensity, it changes the amplitude of the trace on the screen! Sadly I cannot source a circuit diagram for it to help trace the fault. I'm not good enough to do it flying by the seat of my pants!
You can buy the 2214 Service Manual CD on Ebay (See Ebay: 371955865214).....it says it contains the schematics.
@@IanScottJohnston Hey Ian. Great tip! Thank you for that! 🤩
Why are there resistors in parallel with the common mode coils? I have never seen that before, what are they doing?
Two common mode chokes, one for AF and the other for RF noise suppression usually.
The resistors are to form a low pass filter with the following capacitors, but the resistors can't pass a lot of current hence the coils in the chokes do that.
@@IanScottJohnston There not really needed though as the coils form the low pass filter, the higher frequency noise sees the high inductance. I mess about with a lot of switch modes and I have never seen it done this way before.
I'm going to have play around on a breadboard with that filter to see if it makes any difference with noise in and out, I'm glad I stumbled upon this video :)
Try various noise frequencies, especially low freq.
I would have thought bringing up a switch mode like the pre-regulator slowly on a variac is a bad idea as it will send the control loop into a spin. If it had auto 240/120 selection even more so.
A chance worth taking rather than possibly doing more damage to the PSU, and hopefully any issues in doing so would already be designed in.......thats my theory anyways.
@@IanScottJohnston Yeah - fair enough - I don’t really know. But I’ve accidentally damaged equipment by running it on 120 when the voltage selector was set for 240. It was a computer supply from memory.
I think everyone should have an analogue CRT scope, gave mine away years ago which I think was a mistake now. 😞
your right ! what a shame ....Squeak !
THat power supply board would have fired up nicely on its own to check all its voltages.
The focus appears to be wrong... there are resistors that drop the HV for the focus control. These resistor are famous for drifting up in value, making it impossible to adjust focus. Suggest putting more resistors in series... so that each resistor will hold back less voltage and will be more stable over time.
It's perfect in person.......the video just makes it look hugely out of focus.
@@IanScottJohnston Okay... but those resistors are famous for drifting high. Always good to check the value when you've got one on the bench.
@@jamesmichener7526agreed.
I have this exact scope and need to change the RIFAs. Please provide a list of those that you found - reference numbers/values/specs/etc. would be great. Please and thank you! Much appreciated!
This is what I used:
1 x RS 869-7466
1 x RS 220-7786
4 x RS 877-3532
Hi!
wait our you still giving out an oscilloscope??? i need one so bad
Yes, it's still available. Please contact me via my website and give me your story etc and I'll see if you qualify for it.
RF transistors for vertical deflection? DC voltage on vertical deflection!? - oh right, not a CRT TV - I may or may not have expected a nice saw-tooth to the tune of 50 Hz.
Kids, bias is only good for circuits, not humans.
3:10. "made in haiti" ???? 🤔🤔🤔
Low labour costs, close to the USA and good trade agreements I would guess……
if i recal that pre regulator component uis an scr not a mosfet!