Tektronix 2225 Repair no vertical - Page 1
Forum section: electronics / repair

author: DeanKindleysides
author_rank: Contributor
timestamp: December 18, 2017, 10:45:57 am
content: Iam a newbie and trying to repair Tektronix scopeThe problem is both traces are visible for a very sort timeThen jump about and disappear of the top of the screenThe vertical knobs have no affect wile the traces are visable or afterthey disappearPressing beam find brings a short trace back to viewAll power supply voltages are therePlease help

author: tggzzz
author_rank: Super Contributor
timestamp: December 18, 2017, 04:47:41 pm
content: There are many "scope repair" threads on this forum.They all start by saying check all the low voltage power supplies for DC voltage and AC ripple.Then look at your particular scope's service manual; Tek have useful fault-finding guides.Safety: know where the high voltages are, and how long they stay high after turning the scope off.

author: DeanKindleysides
author_rank: Contributor
timestamp: December 18, 2017, 08:44:24 pm
content: Power supply caps replaced dc voltages all in spec and checked for ripple.

author: tggzzz
author_rank: Super Contributor
timestamp: December 18, 2017, 08:58:10 pm
content: Quote from: DeanKindleysides on December 18, 2017, 08:44:24 pmParagraph 3,https://entertaininghacks.wordpress.com/library-2/good-questions-pique-our-interest-and-dont-waste-our-time-2/

author: wasyoungonce
author_rank: Frequent Contributor
timestamp: December 18, 2017, 09:22:06 pm
content: You need a circuit diagram:http://w140.com/tekwiki/wiki/2225First check your PSU voltages again when the problem occurs. Can you also measure EHT voltage?Also maybe look here:https://www.eevblog.com/forum/chat/tektronix-model-2235-anusm-488-repair-and-calibration/https://www.youtube.com/playlist?list=PLK_zQ6_j4TF39mU6Y8Amc7zo39bxU4IhXThere are also lots of threads on this forum regarding this scope.https://www.eevblog.com/forum/repair/problems-with-my-scope-tektronix-2225-horizontal-amplifier/msg1307196/#msg1307196https://www.eevblog.com/forum/repair/tek-2225-scope-repair/msg1347699/#msg1347699

author: DeanKindleysides
author_rank: Contributor
timestamp: December 19, 2017, 09:40:36 am
content: Ok thanksWill dig deeperGoing to check with circuit diagramThought it might have a common fault (quick fix)

author: bd139
author_rank: Super Contributor
timestamp: December 19, 2017, 12:18:28 pm
content: Definitely check power supply voltages. I just refurbed one of these and ALL of the Philips axial capacitors in it were dead or dying so I just shotgunned the entire thing and it's working perfectly now.You don't need to worry about EHT voltage checks on these - entirely not needed unless the intensity pot is shot.The 2225 service manual is freely available (google) and the voltage rails are brought out nicely onto the main board as jumper wires. There is a power supply fault isolation procedure in the manual as well if you find that rails are down.Also the best place to post is here:http://groups.io/g/TekScopes2Edit: you can see the jumper wires at the top left (and all the replaced capacitors):As you're in the UK, CPC are the best place to buy cheap replacement caps. Vishay 030 are suitable replacements for the axial ones (the blue ones). I did the rest with Rubycon and EPCOS. EPCOS one is the main filter cap and had to be purchased from RS.

author: DeanKindleysides
author_rank: Contributor
timestamp: December 19, 2017, 03:28:03 pm
content: Thanks I will replace the axial caps next