Tektronix 2213 Hum Problem
jh...@my-deja.com
have a fairly loud hum coming from the large AC power line choke
mounted on the inside back panel of the chassis. I did a quick check of
the ESR's of all the electrolytic filter caps in the power supply and
they seem reasonable. I can't believe that this is just bad design from
Tektronix and there must be some fix for it. Both scopes seem to work
fine except for the annoying hum. By the way, I've seen at least 2
scopes of this type listed on Ebay that describe this same problem. Are
there any Tektronix experts out there who have run across this problem
and could offer some advice?
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Before you buy.
Asimov
Tektronix 2213 Hum Problem (02 Nov 99 00:22:46)
jh> I have a Tektronix 2213 oscilloscope (and a 2215 scope too) that both
jh> have a fairly loud hum coming from the large AC power line choke
jh> mounted on the inside back panel of the chassis. I did a quick check
jh> of the ESR's of all the electrolytic filter caps in the power supply
jh> and they seem reasonable. I can't believe that this is just bad design
jh> from Tektronix and there must be some fix for it. Both scopes seem to
jh> work fine except for the annoying hum. By the way, I've seen at least 2
jh> scopes of this type listed on Ebay that describe this same problem.
jh> Are there any Tektronix experts out there who have run across this
jh> problem and could offer some advice?
You have to expect that something that draws substantial current will
have some magnetoconstrictive effects on iron cores. Try installing a
tension band, a U-bolt, a hose clamp, tighten the screws harder. But you
might simply try mounting the offending device on a loose base such as
using rubber grommets to isolate it from the main chassis. Perhaps a
little box over the part could contain airborne sound. Is it really that
loud? Try a white noise generator, turn up the music, listen to the
radio...? <G>.
... A stereo system is the altar to the god of music.
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Jim Yanik
>
>jh...@my-deja.com said the following to All on the subject of
>Tektronix 2213 Hum Problem (02 Nov 99 00:22:46)
>
> jh> I have a Tektronix 2213 oscilloscope (and a 2215 scope too) that both
> jh> have a fairly loud hum coming from the large AC power line choke
> jh> mounted on the inside back panel of the chassis. I did a quick check
> jh> of the ESR's of all the electrolytic filter caps in the power supply
> jh> and they seem reasonable. I can't believe that this is just bad design
> jh> from Tektronix and there must be some fix for it. Both scopes seem to
> jh> work fine except for the annoying hum. By the way, I've seen at least 2
> jh> scopes of this type listed on Ebay that describe this same problem.
> jh> Are there any Tektronix experts out there who have run across this
> jh> problem and could offer some advice?
>
>You have to expect that something that draws substantial current will
>have some magnetoconstrictive effects on iron cores. Try installing a
>tension band, a U-bolt, a hose clamp, tighten the screws harder. But you
>might simply try mounting the offending device on a loose base such as
>using rubber grommets to isolate it from the main chassis. Perhaps a
>little box over the part could contain airborne sound. Is it really that
>loud? Try a white noise generator, turn up the music, listen to the
>radio...? <G>.
>
this hum is characteristic of the early 2200 series. There was a mod developed
for this that removed the SCR pre-regulator circuitry and installed a PWM
pre-reg circuit board,but they are long unavailable. There even waw a rubber
cushion that TEK tried to reduce the hum,it went between the choke and the
chassis,but not very effective. Maybe you could find a 2213/15 that HAS the PWM
pre-reg assy,but non-repairable otherwards,and install it in your scope,but
then you would need the mod instructions to know what parts to clip off the
motherboard.Hey,I might still have them!I think I have the manual insert,but
I'm not sure about the mod instructions.
Jim Yanik,NRA member
RWatson767
>: Re: Tektronix 2213 Hum Problem
Do you have a manual for a 2213?
Bob AZ
Jim Yanik
says...
No,I have the 2215 manual.But,curiously,I have a 2213!(I built it myself from a
mix of 2213 and 2215 boards) I would suggest trying to isolate the choke from
the rear chassis by using some rubber washers and longer bolts. Watch out for
those tiny TorX screws,IIRC,they're T-6 size.
Jim Yanik,NRA member
jh...@my-deja.com
mounting/isolation schemes but none are satisfactory. The hum is a
combination of the winding on the E core ,the sheet metal shield around
the choke and the mounting of the choke to the big sounding plate (the
back panel of the scope!). Short of potting the whole assembly and
suspending it inside the case, I think the Pre-Reg Triac to PWM is the
answer but it's not worth the trouble for those scopes. I will just
sell them with the bonus "Audible ON" indicator feature! It really is
an annoying hum and Tek's rubber pad fix is quite amusing. Now, If
someone could just help me find that stupid 155-0241-01 Hor Amp IC, I
could get my 2445 back in service......