Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: Contributors :: Advertise


It is currently May Mon 28, 2018 12:17 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 14 posts ] 
Author Message
 Post subject: Heathkit 0-5 Oscilloscope(s)--FINALE
PostPosted: Jun Sat 20, 2009 10:18 pm 
Member
User avatar

Joined: Mar Thu 20, 2008 4:02 pm
Posts: 2394
Location: Prescott AZ
Hello all,
This is a new thread to update all of you who helped me with my very long thread (ended about a week ago) trying to rebuild my 1950 Heathkit 0-5 oscilloscope.

When I left off the last thread I had purchased a second 0-5 for parts and also a repro manual. Today I received both of them. The circuit diagram showed that you guys were "on the money" in making your diagnosis and suggesting measurements I should make even without the proper schematic.

The parts oscilloscope came with a 5BP4 CRT (white trace instead of green). Substituting that tube for my 5BP1 seems to have solved the problem. The 5BP4 is well used so I need to have the intensity pot up near the max to get a nice trace BUT the trace does not dim after a min or two and, in fact, stayed the same for 10 min that I tried it.
So now I have looked at three CRTs for this scope. The original 5BP1 which was very dim right from the start; the replacement 5BP1 purchased a while ago online which may be gassy? because it starts out quite bright and then gets very dim after a min or two and stays very dim; and finally the replacement 5BP4 which came with the parts oscilloscope which is in the middle in terms of brightness BUT it doesn't change and is quite useable if I keep the room fairly dim.

The parts oscilloscope turns out to be complete and untouched as far as I can tell since 1950. It has all original caps and resistors and a horribly rotted line cord. It has not been plugged in for a long long time based on the very rotted line cord. I think I will replace the line cord and make some careful tests with this scope . It may be that I will rebuild this one as well......why not? It's not a very useful scope but it has survived 59-60 years and I think it is worth the attempt. I did notice that all the components and pots have some sort of white coating on them which, if I didn't know better, I'd think might be mildew but I don't smell the "mildew" odor. This bears some further investigation before I go too far.

Thanks again to all of you for your advice, suggestions and help keeping this scope novice in the game.
Mark


Last edited by retiredinprescott on Jun Wed 24, 2009 10:31 pm, edited 1 time in total.

Top
 Profile  
 
 Post subject:
PostPosted: Jun Sun 21, 2009 2:47 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 3036
Location: Seattle WA US
Your scope may have spent a long time in a damp place. Suggest you rig a way to warm it to around 120 degrees and let it sit there for several days, just to get any moisture out - before you attempt to apply power.

--Chuck


Top
 Profile  
 
 Post subject:
PostPosted: Jun Sun 21, 2009 2:51 am 
Member
User avatar

Joined: Mar Thu 20, 2008 4:02 pm
Posts: 2394
Location: Prescott AZ
Chuck,
Luckily I live in central Arizona these days. 10% humidity and tons of sunshine. I'll put the scope (minus the case) outside during the day for a couple of days. That should do it. My wife quickly vetoed the oven idea.

I also found a source for a 1000VDC oil capacitor (about 2uf) of the right size to replace the original one in the scope now.
That should get me started.
Thanks,
Mark


Top
 Profile  
 
 Post subject:
PostPosted: Jun Sun 21, 2009 5:09 am 
Member

Joined: May Tue 30, 2006 7:28 am
Posts: 4576
Location: Southern Ga. zip 31768 US
Glad your back with it, the humidity in this area is like walk outside and your soaked.

_________________
Rodney


Top
 Profile  
 
 Post subject:
PostPosted: Jun Sun 21, 2009 7:30 am 
Member
User avatar

Joined: Nov Tue 18, 2008 8:34 am
Posts: 1230
Location: Hutchinson,Kansas
Good for you! I have an O-11 I am gonna tinker with here sometime. It sorta works. Got a manual and stuff on the way for it!


Todd


Top
 Profile  
 
 Post subject:
PostPosted: Jun Sun 21, 2009 3:05 pm 
Moderator
User avatar

Joined: Feb Sun 01, 2009 2:56 pm
Posts: 9486
Location: Victoria, Australia
Good to know that the CRO is now working.

Now that you have the book, sorting out the second one should be "a walk in the park".

I would follow the dryout idea. Pull the rectifiers & check the transformer. If it's all good..... go for it with the refit.

Clean it wearing a respirator as you don't know what the powder is; Even Mildew inhaled can be dangerous.

Marc


Top
 Profile  
 
 Post subject:
PostPosted: Jun Sun 21, 2009 10:56 pm 
Member
User avatar

Joined: Mar Mon 17, 2008 5:05 am
Posts: 5204
Location: Ashhurst, New Zealand
The white stuff is probably the cadmium plate going off - oxidation. The powder is nasty - the procedure I use is a stiff paintbrush and a vacuum cleaner nozzle close by - seal the bag and throw it in the garbage when you've finished. Don't tell the greenies or they'll have the Environmental Protection Agency around to have you taken away!

_________________
Cheers - Martin ZL2MC


Top
 Profile  
 
 Post subject:
PostPosted: Jun Mon 22, 2009 1:47 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 1570
Location: St. Paul, Minnesota
Nolan Lee had an innovative way to dry out transformers posted on his site, it you find moisture or other hard-to-explain problems remain after you've given the 'scope a good suntan. Seems like somebody here is hosting an archived copy of his site....

If you can't find that, and if you find your transformers won't dry out, I'll look for the Nolan Lee method, I may have printed it way back when. It was classic Nolan Lee, and very effective.


Top
 Profile  
 
 Post subject:
PostPosted: Jun Mon 22, 2009 4:21 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 7697
Location: Beaver Falls, PA. USA
Too bad the 5BP4 is weak; that tube will fit at least one early British TV. Maybe someone would do a swap for you with a 5BP1...

_________________
Tim KA3JRT


Top
 Profile  
 
 Post subject:
PostPosted: Jun Mon 22, 2009 4:26 am 
Member
User avatar

Joined: Mar Thu 20, 2008 4:02 pm
Posts: 2394
Location: Prescott AZ
The 5BP4 CRT is the best one I have. I am using it in the scope I rebuilt. I put the second best one (a 5BP1) in the second Heathkit 0-5 and I've started working on that scope. I replaced the electrolytic caps so far and checked the 1uf, 1000V oil filled cap. I can get a spot on the CRT but the sweep doesn't seem to work. I have yet to replace any of the paper caps and check all the resistors. That will be next.
Mark


Top
 Profile  
 
 Post subject:
PostPosted: Jun Wed 24, 2009 10:39 pm 
Member
User avatar

Joined: Mar Thu 20, 2008 4:02 pm
Posts: 2394
Location: Prescott AZ
I now have both Heathkit 0-5 scopes rebuilt and functioning OK.
The final problem I resolved was with five micamold 6800pf capacitors in each scope. I initially assumed they were mica capacitors and did not replace them.
There is a thread about these capacitors in the electrical/mechanical restoration forum entitled " Bad Micamold 6800pf capacitors?"
It turns out that ALL of these capacitors were bad in both scopes and when I disected one, it was a paper/foil capacitor in a square moulded case designed to look like a mica capacitor. Live and learn, I guess.
Anyway, changing out those capacitors (one in the sweep frequency switch and four across the four 6SH7 tubes between filament and cathode) didn't really change the way any of the CRTs I've described before behaved but the scopes are well behaved now and pretty stable. Good enough for a 1950 vintage, low end scope.
I'm happy with the outcome and thanks again for everyone's help.
Mark


Top
 Profile  
 
 Post subject: Re: Heathkit 0-5 Oscilloscope(s)--FINALE
PostPosted: Feb Sat 03, 2018 1:03 am 
New Member

Joined: Apr Mon 17, 2017 4:26 pm
Posts: 2
Hello all,

Can someone share the Heathkit Model O-5 Oscilloscope schematics or manual?

I am trying to resurrect one so I will appreciate all the help you can provide.

Thanks for your time!


Top
 Profile  
 
 Post subject: Re: Heathkit 0-5 Oscilloscope(s)--FINALE
PostPosted: Feb Sat 03, 2018 7:58 am 
Member
User avatar

Joined: Nov Mon 02, 2009 7:01 am
Posts: 2708
Location: Lincoln City, OR
Greetings to Mark and the Forum:

I have a couple of N.O.S. 5UP1's. I don't know if they will sub for the 5BP1 or not, but if so and you are interested, PM me.

Regards,

_________________
Jim T.
KB6GM


Top
 Profile  
 
 Post subject: Re: Heathkit 0-5 Oscilloscope(s)--FINALE
PostPosted: Feb Sat 03, 2018 11:01 am 
Moderator
User avatar

Joined: Feb Sun 01, 2009 2:56 pm
Posts: 9486
Location: Victoria, Australia
From personal experience with "Micamold" anything with Micamold on it should be treated with the same contempt as a Waxed Paper cap: "Micamold" on a cap, or resistor, is its brand and in many caps, is not to be confused with Mica: The mineral & dielectric.

Marc


Top
 Profile  
 
Post New Topic Post Reply  [ 14 posts ] 

All times are UTC [ DST ]


Who is online

Users browsing this forum: Exabot [Bot], shawn1967 and 8 guests



Search for:
Jump to:  
























Privacy Policy :: Powered by phpBB