Fun! Well done. My 2235 was perfect for about a year, now, my X-Y mode has failed. I’m seeing a very slow and delayed trace instead of a steady dot or line from my DIY curve tracer. I need to hit the manuals I guess. They are first rate.
Very nice repair job. Thanks for contributing to the survival of these wonderful Tek scopes. How did you know the exact parts number of the new diode that you ordered? Was it written in the manual? Did you find a diode with the exact same parts number or did you use a substitute? In this case, I don't think it matters much if you don't find a diode with the exact same parts number since it's only used as a clamping diode anyway. Reverse breakdown voltage of the new diode should be taken into consideration since we're talking about a 100V rail, and the waveform should be checked after the new diode is installed to make sure that the parasitic capacitance of the new diode isn't causing a problem. (Not likely it will, but it's best to check.) A short recovery time wouldn't hurt either, I guess. A 1N4148 is not good enough in this case since it's rated at a maximum reverse voltage of only 75V. I have a fully working Tektronix 2235 as well. If anyone ever needs measurements or waveforms from a working 2235, let me know and I might be able to help you out.
The part number is listed on the service manual and also once I removed the defective diode I was able to read the part number on the device itself which agreed with the manual. I bought an exact replacement from ebay and thankfully it wasn't a fake. Actually the original diode is 1N4152 with peak reverse repetitive voltage of 40V which is much more less than the 1N4148 (Vrrm = 75V). If you can see on the schematic, the clamping diode doesn't see the 100V rail so breakdown during normal operation isn't an issue. I think the diode is meant to protect the reverse breakdown of the base to emitter diode of the transistor Q845. You can also see a similar diode attached to the base of the bottom transistor(Q840) to ground. As far parasitic capacitance is concerned the 1N4184 has 4pF while the original 1N4152 has 2pF. So they are comparable. Regardless I have removed the 1N4148 and replaced it with the proper 1N4152 diode.
I wish I could help but I don't have that scope. But here is a link that you might find useful from eevblog fourm inregards to Hameg 408-1A repair: www.eevblog.com/forum/testgear/hameg-408-1a/ Also read up on this Tektronix general scope repair & troubleshooting guide: www.sphere.bc.ca/test/tek-parts/troubleshooting-scopes.pdf Good luck!
Just want to say nice lab and I love all the equipment, especially the boat anchor gear. Not a single modern LCD/LED oscilloscope in sight. LOL. I work as an electronics technician and electronics is also my hobby and i`m also a ham radio operator. Is that your real name or did you name yourself after the old school equipment maker named Smith Corona. I think they made those big clunky typewriters. Keep up the good work. KD6CFE was here . 73`s
Thank you very much sir! I love old gear specially CRT based oscilloscopes. I hate to see them end up in the land fill. Regarding the name, I was never aware there was a typewriter manufacturer named similar to my name. Thanks for bringing that to my attention.
You probably dont care but if you are bored like me atm then you can stream pretty much all of the latest movies on InstaFlixxer. I've been watching with my gf for the last few weeks =)
i have the same scope and in the same situation but i don't have another scope to check the waveform, anyway i might comeback to you with some questions, thank you.
Good job! I'm awaiting delivery of a Tek 2235A a childhood dream come true :D
Thank you and I am happy for you that you got the scope!
After 5 years, are you still using it? I have one of those as well. Works great for me!
Fun! Well done. My 2235 was perfect for about a year, now, my X-Y mode has failed. I’m seeing a very slow and delayed trace instead of a steady dot or line from my DIY curve tracer. I need to hit the manuals I guess. They are first rate.
Great job!
I have this scope, much to learn. Have downloaded this manual also. ThankYou
Great repair, thanks for sharing!
Very nice repair job. Thanks for contributing to the survival of these wonderful Tek scopes. How did you know the exact parts number of the new diode that you ordered? Was it written in the manual? Did you find a diode with the exact same parts number or did you use a substitute? In this case, I don't think it matters much if you don't find a diode with the exact same parts number since it's only used as a clamping diode anyway. Reverse breakdown voltage of the new diode should be taken into consideration since we're talking about a 100V rail, and the waveform should be checked after the new diode is installed to make sure that the parasitic capacitance of the new diode isn't causing a problem. (Not likely it will, but it's best to check.) A short recovery time wouldn't hurt either, I guess. A 1N4148 is not good enough in this case since it's rated at a maximum reverse voltage of only 75V.
I have a fully working Tektronix 2235 as well. If anyone ever needs measurements or waveforms from a working 2235, let me know and I might be able to help you out.
The part number is listed on the service manual and also once I removed the defective diode I was able to read the part number on the device itself which agreed with the manual. I bought an exact replacement from ebay and thankfully it wasn't a fake.
Actually the original diode is 1N4152 with peak reverse repetitive voltage of 40V which is much more less than the 1N4148 (Vrrm = 75V). If you can see on the schematic, the clamping diode doesn't see the 100V rail so breakdown during normal operation isn't an issue.
I think the diode is meant to protect the reverse breakdown of the base to emitter diode of the transistor Q845. You can also see a similar diode attached to the base of the bottom transistor(Q840) to ground. As far parasitic capacitance is concerned the 1N4184 has 4pF while the original 1N4152 has 2pF. So they are comparable. Regardless I have removed the 1N4148 and replaced it with the proper 1N4152 diode.
hi...let me say...you are the best (i have the same problem with my hameg 408,and another one more )
Thank you! Did you fix your hameg 408?
@@SmithKerona Unfortunble,i don.t.I need some help...Thancks for responding.
I wish I could help but I don't have that scope. But here is a link that you might find useful from eevblog fourm inregards to Hameg 408-1A repair: www.eevblog.com/forum/testgear/hameg-408-1a/
Also read up on this Tektronix general scope repair & troubleshooting guide: www.sphere.bc.ca/test/tek-parts/troubleshooting-scopes.pdf Good luck!
Just want to say nice lab and I love all the equipment, especially the boat anchor gear. Not a single modern LCD/LED oscilloscope in sight. LOL. I work as an electronics technician and electronics is also my hobby and i`m also a ham radio operator. Is that your real name or did you name yourself after the old school equipment maker named Smith Corona. I think they made those big clunky typewriters. Keep up the good work. KD6CFE was here . 73`s
Thank you very much sir! I love old gear specially CRT based oscilloscopes. I hate to see them end up in the land fill.
Regarding the name, I was never aware there was a typewriter manufacturer named similar to my name. Thanks for bringing that to my attention.
You probably dont care but if you are bored like me atm then you can stream pretty much all of the latest movies on InstaFlixxer. I've been watching with my gf for the last few weeks =)
@Dakari Maxton Definitely, I have been using InstaFlixxer for months myself :)
i have the same scope and in the same situation but i don't have another scope to check the waveform, anyway i might comeback to you with some questions, thank you.