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Damaged 606

Lars Brinkhoff
 

Hello,

I bought a Tektronix 606 off eBay. When I tested it I get this:

https://imgur.com/a/cLOaOVu

There's a bright spot fixed at the center. There's a movable spot, or
short line pointed towards the center, which is to the lower left in the
photo. Between the two is a squiggly line.

I'm a bit out of my depth here. What could cause this? Any advice
would be welcome.

satbeginner
 

Looks as damage to the internal electron gun supports, CRT is toast :-(

toby@...
 

On 2020-01-21 3:16 PM, satbeginner wrote:
Looks as damage to the internal electron gun supports, CRT is toast :-(
The symptoms seem similar to my 604 that I posted about on 16 Jan.

I'm not an expert by any means but my guess was also internal damage
(broken weld etc) -- and my unit had clearly had a severe blow, enough
to chip a corner off the CRT (without breaking vacuum though).

Any more input greatly welcomed.

--Toby


Lars Brinkhoff
 

satbeginner wrote:
Looks as damage to the internal electron gun supports, CRT is toast :-(
Thank you, that makes sense.

I measured the outputs from the low voltate power supplies. Some are of
out of spec, especially -30V. But I'm not sure that would explain the
problem.

-30V is -17.1 (should be at least -29.1)
+15V is +14.9 (ok)
+30V is +27.5 (ok)
+120V is +100.8 (should be +108)
+270V is +261.7 (close, at least +262)

Stephen Hanselman
 

Check the AC on those PS, we see these go bad often

Regards,

Stephen Hanselman
Datagate Systems, LLC

On Jan 21, 2020, at 22:47, Lars Brinkhoff <lars@...> wrote:

satbeginner wrote:
Looks as damage to the internal electron gun supports, CRT is toast :-(
Thank you, that makes sense.

I measured the outputs from the low voltate power supplies. Some are of
out of spec, especially -30V. But I'm not sure that would explain the
problem.

-30V is -17.1 (should be at least -29.1)
+15V is +14.9 (ok)
+30V is +27.5 (ok)
+120V is +100.8 (should be +108)
+270V is +261.7 (close, at least +262)


 

Always get the power supplies working first. Looks like you need to replace some electrolytics.

On 1/22/2020 1:47 AM, Lars Brinkhoff wrote:
satbeginner wrote:
Looks as damage to the internal electron gun supports, CRT is toast :-(
Thank you, that makes sense.

I measured the outputs from the low voltate power supplies. Some are of
out of spec, especially -30V. But I'm not sure that would explain the
problem.

-30V is -17.1 (should be at least -29.1)
+15V is +14.9 (ok)
+30V is +27.5 (ok)
+120V is +100.8 (should be +108)
+270V is +261.7 (close, at least +262)

Roger Evans
 

Before you give up all hope, check for very large values of ripple on the -30V and +120V supplies. The bulk smoothing capacitors can go low capacitance / high ESR with age and you get almost 100% modulation of the raw DC into the low voltage regulator. As a quick fix you can just tack on an external capacitor in parallel, even on long leads, to see if the distorted trace returns to something more nearly normal.

The -30V biasses the X and Y amplifiers and if it goes way out of spec twice every mains cycle you will see the spot trace out a possibly complex shape as the amplifier operating point changes. I saw something similar on a 475 with three power rails showing large ripple and the timebase not working due to an open circuit switching transistor.

Roger

 

Hi:
Check first , my 606B also had the problems, even the small value E-Cap !
Rd
Tony C

從我的iPhone傳送

Stephen Hanselman <kc4sw.io@...>於2020年1月22日 15:29寫道:

Check the AC on those PS, we see these go bad often

Regards,

Stephen Hanselman
Datagate Systems, LLC
On Jan 21, 2020, at 22:47, Lars Brinkhoff <lars@...> wrote:

satbeginner wrote:
Looks as damage to the internal electron gun supports, CRT is toast :-(
Thank you, that makes sense.

I measured the outputs from the low voltate power supplies. Some are of
out of spec, especially -30V. But I'm not sure that would explain the
problem.

-30V is -17.1 (should be at least -29.1)
+15V is +14.9 (ok)
+30V is +27.5 (ok)
+120V is +100.8 (should be +108)
+270V is +261.7 (close, at least +262)