Tek 2230 psu story (work in progress)


Pitpat
 

Hi! im currently fighting with a Tek 2230 that really don't want to come back from the graveyard, i'm posting this hoping that my experience may one day help someone else.
So... i've got it from an auction in a pretty common state, It had a gone fuse, q9070, cr907 and the full first rectifing section.
I replaced all the busted components and it got in the famous ticking state indicating that the the crowbar circuitry got in action. (at least it had some life)
I then removed all the electrolitics to be esr checked and sure enough few of them tested really tired, after that i then replaced the bad ones and resoldered the few that passed the test back in place (my first mistake),
Since i loose half of the few neurons that i still have when it comes to stay up late at night i connected backwards the q9070 connector and surprise... all the 908 components bursted in a big zap and with them the u930 :(
Another trip to the local supply (20 km from home, fair enough...) and the scope got back in his sobbing state, i then tried to feed the 42v from the testing points, nothing, the external psu reported a 4A current that toasted the shunt resistor of the scr.
Since the situation started to get a bit serious i then checked all the components of the pre-regulator and the inverter that indeed tested fine. So the problem is in the hv trafo t948 i thought, it must be... I poceded to remove it (PITA) and sure enough i got my 42v back.
At this point i couldn't do more since I ain't got no way to test the trafo and replacements seems to be a bit rare to come by so i decided to try the one last thing... remove the scr isolate all the psu and solder back in place the t948 with some wire.
It got back to life! (almost...) the HV multiplier is still disconnected the fan lightly spin and all the reference voltages aren't in spec.
I then replaced one of the four 'litics (i had only one in stock) that i didn't and the fan spinned a bit more and the voltages seems to be moved a bit towards the specs ones.
Thats all, for now... i'll keep this thread updated.


PS. Please be kind on my english, i do understand it pretty good but i don't really practice my speak-write ability at all so take it with a grain of salt!
Ciao!
Pit.


tekscopegroup@...
 

About 12 years ago I repaired a 2213A power supply and the main problem was T948. So basically yes, you are probably correct in your assumption that your T948 is bad as well, as it has happened before. Before getting a replacement donated from another member I really tried the all usual everything under the sun checks and part replacements to try and fix the problem but of course nothing worked and in the process I rather ended up also burning some freshly replaced components. I think you need to search for a parts/junked 22xx scope or just the main board as I was lucky enough to get it, and hope T948 is good and move ahead by replacing it. This power supply is extremely finicky and temperamental, and very intolerant of mistakes, there is no middle ground, its either fully working or not. In the end in my case it was the very last part I replaced that fixed everything after about 6 weeks of hunting down the cause.


satbeginner
 

I recently had a bad transformer in my 2235A.
I posted a thread on the repair and a link to an album.

I proved the transformer was bad by the simple to perform Ringing test...

Pictures are in the album.

Sorry, I'm on my phone, so not so easy to find and post the link.

Look for 2235 repair by my, Satbeginner.

Saludos,

Leo


Pitpat
 

Hi thanks for the replies! I've found a t948 new-old stock, with the original box! and sinece it is already in my country I really couldn't resist.. it should be here by the end of the week.
I think I've already seen Leo's post few days ago but i'll for sure have a second glance at it since back in the days T948 wasn't on my suspects list... and maybe post some photos of my attempt with the ringing test :)
Again I'll keep this thread up.
Ciao.
Pit


PS Couldn't notice the dingy boat in Leo's profile pic. and since i'm a small-boat saylor too it put a a big smile on my face! Always good to find other sea lovers! Will you see the America's cup finals tonight? I'm team Lunarossa hehe.
Again, Ciao
Pit from Italy.


Pitpat
 

Update, the new t948 has arrived but not before i managed to burst another componet, a zener diode this time (1N475A) 6.2 voltage reference in the inverter section seems to be the only fault this time but since im at it ill replace all the electrolitic caps with some new good low esr ones. BTW the fail (open not shorted) of the said diode seems to result in a similar cycle of the one induced by the crowbar circuit (witch it was removed on my scope) but with the neon spark-gaps that do not operate.