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Author Topic: Tubular capacitor in HW-101?  (Read 4857 times)
N4NYY
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« on: October 18, 2010, 05:13:27 PM »

This is a 1uf tubular cap on the bottom  side of the chassis. It is banded.

Question is, should I replace this in a restore, like the electrolytics?

Secondly, why is this banded? I didn't know these were polarized.
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AC5UP
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« Reply #1 on: October 18, 2010, 06:43:02 PM »

Does the cap you're referring to look like this: http://www.tone-lizard.com/images/Black_Beauty.jpg ?

If so, it's likely a .1uf paper jobbie and should be replaced. Double check the value and voltage on the schematic. As for polarity, there is none but the new cap should have a black mark near one end denoting the outside foil. As a general rule the outermost layer of foil should be on the side nearest to ground.

Long ago and far away the old wax paper caps would become difficult to read after the wax darkened so the industry came up with a six band color code for caps. The bench techs at the time were not impressed as the voltage & tolerance rings made them easy to misread.
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N4NYY
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« Reply #2 on: October 18, 2010, 07:05:24 PM »

No. It is the one here in the lower right next tothe 2 cans, yellow with "Electro Cube" label.

http://www.radioremembered.org/images/hw101/hw101-17.jpg
« Last Edit: October 18, 2010, 07:56:30 PM by Vinnie Sallustio » Logged
AC5UP
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« Reply #3 on: October 18, 2010, 08:15:23 PM »

No. It is the one here in the lower right next tothe 2 cans, yellow with "Electro Cube" label.

http://www.radioremembered.org/images/hw101/hw101-17.jpg

Yokay... I think that's a Mylar cap and I've had no problems with them. Very common part in the 70's & 80's, BTW. Test it if you like, but as far as an automatic replace... Nope. Not on that one. The black band on the left side (near the E in Electro) indicates the outside foil.
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N4NYY
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« Reply #4 on: October 18, 2010, 08:29:15 PM »

Cool, thanks! This is for a friend that I am restoring. Really, the thing is in fine shape. He is paying me by giving me an SB-200, that needs restoration. That one will need work.
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KE4JOY
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« Reply #5 on: October 19, 2010, 06:17:17 AM »

Are you just going through it and replacing everything that 'might' be bad?

I know that shotgunning is popular these days but it wont teach you about how the circuit works or even what might actually be wrong.

Sure you might get lucky and end up replacing an open or shorted cap or a fried resistor but even if you shotgunned every diode, cap, resistor, in the rig your still going to have to align it. Alignment of a 101 is no small feat as the plate/grid circuits are 'series tuned' meaning they have to be tuned in a specific order or you will just be chasing your tail.
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N4NYY
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« Reply #6 on: October 19, 2010, 08:29:05 AM »

Quote
Are you just going through it and replacing everything that 'might' be bad?

I know that shotgunning is popular these days but it wont teach you about how the circuit works or even what might actually be wrong.


No. I am not shotgunning and it may work fine. I have not even turned it on yet. There is one known problem with this. The VFO is not oscillating. This is a project that another ham gave me as an educational experience, He has far more knowledge than I do and this was his restore project. But he let me do it for him. I typically replace all the electrolytics, wax, paper, some carbon composite resistors, etc. I was not familiar with capacitor in question. Once I do that, then I check operation and troubleshoot.
 
He has given me a VFO, that was still in the box unopened. However, it has moisture damage and corosion. Since the box was not showing any moisture damage, I assumed it was sold to him in that manner. He got screwed. I will try and rebuild the VFO. If that don't work, it appears they are fairly cheap and I can buy one.

The alignment is the very last thing I perform after everything is verified to be working, and I have completed everything else like re-capping. cleaning, etc. 
« Last Edit: October 19, 2010, 08:38:19 AM by Vinnie Sallustio » Logged
W5RKL
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« Reply #7 on: October 19, 2010, 10:51:38 AM »

Quote
No. I am not shotgunning and it may work fine....I typically replace all the electrolytics, wax, paper, some carbon composite resistors, etc. I was not familiar with capacitor in question. Once I do that, then I check operation and troubleshoot.

You replace components without any evidence indicating the components need to be replaced yet you say you are not shot gunning component replacement. I'm sorry but you are shot gunning component replacement and that is very poor practice. How do you determine when a component should be replaced? How do you determine when to replace an electrolytic capacitor? Because the components are old? If that's your method then that is very poor troubleshooting and repair practice!

Quote
I have not even turned it on yet. There is one known problem with this. The VFO is not oscillating.

What steps were taken to determine the VFO is actually not oscillating?

Quote
I will try and rebuild the VFO. If that don't work, it appears they are fairly cheap and I can buy one.

You are going to rebuild a VFO without any troubleshooting or taking any steps to determine "why" the VFO is not working? Why?

Mike
W5RKL
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N4NYY
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« Reply #8 on: October 19, 2010, 11:23:14 AM »

Quote
You replace components without any evidence indicating the components need to be replaced yet you say you are not shot gunning component replacement. I'm sorry but you are shot gunning component replacement and that is very poor practice. How do you determine when a component should be replaced? How do you determine when to replace an electrolytic capacitor? Because the components are old? If that's your method then that is very poor troubleshooting and repair practice!

Holy crap. Have you ever heard of re-capping? Which is essentially what I am doing? There are loads of websites on this. I have not troubleshot this. I was simply re-capping first. Read the initial question. The question was about a cap and if it needs replacement, like electrolytics. It said nothing about whether it being bad. That is very poor practice? Re-capping is a bad practice?

Quote
What steps were taken to determine the VFO is actually not oscillating?
The owner told me as such. It was his restore project and he gave to me. He even supplied me with a spare VFO. Are you following the thread?

Quote
You are going to rebuild a VFO without any troubleshooting or taking any steps to determine "why" the VFO is not working? Why?

Because the owner told me such. Which is why he supplied me a spare. It appears he had already troubleshot that part of the rig.

« Last Edit: October 19, 2010, 11:26:36 AM by Vinnie Sallustio » Logged
N4NYY
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« Reply #9 on: October 19, 2010, 12:06:34 PM »

FWIW, let me explain something. For the first time yesterday, I opened up a HW-101 and PS-23 power supply. I did a visual. I noticed some burnt looking resistors. Caps look old. There is a Heathkit factory service tag dated 1978. I took an inventory of the parts, specifically, the caps. I plan on re-capping, and also replacing some of the burnt looking resistors, even before I power it up. That is right. I have not fired anything up as of yet. In fact, this power supply is the first HV power supply I have ever touched or looked at, in my life. I know of one problem, which the owner tells me, is that the VFO is not oscillating. He provided a spare. The spare looks bad from moisture damage. That ends my visual inspection.

Based on that, and on this thread that simply asked to identify one cap, I have been labeled a shotgunner troubleshooter and have poor troubleshooting techniques! Hell, I didn't even know you could even troubleshoot without firing up the rig, first.

Thanks!
« Last Edit: October 19, 2010, 02:36:29 PM by Vinnie Sallustio » Logged
KB4QAA
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« Reply #10 on: October 19, 2010, 12:25:23 PM »

Sounds to me like you are doing fine.  Makes sense to replace the electrolytic and tubular caps as well as toasty looking resistors(of which there will be a few in any Heathkit).   Keep going.

And heck, if you feel like replacing every component with new, do it!  "You will have to realign it".  So what.  You'll have to realign it anyway!

Sheesh. 
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N4NYY
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« Reply #11 on: October 19, 2010, 12:46:21 PM »

KB4QAA, the person paid me with a SB-200 amp. The amp needs work and was another of his restore projects. He said I can have it because of the work I will do for him on the HW-101. I haven't so much as lifted the cover on it yet. Also, that will be my very first amplifier that I have ever had my hands on. My previous experience with amplifiers (aside from those already in transceivers), were small signal non-RF amps from my tech school days in the mid 1980's.

And believe me, I will probably not even bother aksing questions about it. I don't need to be taking additional beatings! Thanks for your words of support  Grin

« Last Edit: October 19, 2010, 12:58:28 PM by Vinnie Sallustio » Logged
K8AC
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« Reply #12 on: October 19, 2010, 02:36:44 PM »

To N4NYY: As someone who has restored maybe 100 radios of all kinds (pre-1950 primarily) and repaired an equal number of all vintages, I support the approach you used.  I didn't do that from the beginning, but I quickly learned that it was extremely time-consuming to troubleshoot radios without doing that as they usually exhibited multiple problems, or there were several causes of the same symptom.  I suppose that approach might make sense to the purists and/or engineers, but it didn't make  any sense to me.  The failure rate of electrolytics as they approach 40 or 50 years of age is extremely high and a failure will often take other components in a power supply out as well.  Likewise, tubular caps of all varieties, from the old wax/paper caps to the plastic "black beauties" are often troublesome, particularly when they're marginally bad.  When restoring any old gear, I routinely replace all the electrolytics and tubular caps and of course any resistors that are visibly cracked or burned open.  I don't wholesale replace resistors and have found that it really doesn't matter whether that old 2 meg resistor that now measures 3 meg is within tolerance or not.  After the cap replacements, 99% of the time the radio works very well with no residual problems.

Replacing electrolytics and tubular caps shouldn't have any effect on alignment.  On the other hand, chances that a previous owner used a "golden screwdriver" approach to troubleshooting is extremely high and alignment might be required for that reason.  And - particularly with Heathkit gear - you can never be sure that the unit EVER worked correctly.  Wiring or component errors are often seen, and the alignment might have never been done correctly in the first place.  The world of restoring/troubleshooting a 40-50 year old piece of gear that has had many owners and perhaps an unskilled builder in the beginning is quite different from troubleshooting a newer factory-assembled piece.  The cost of replacing all the caps is very low and can be done rather quickly in most cases.  While some very knowledgeable and respected folks strongly disagree with the approach, it sure works for me and frees up time for other projects. 
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N8CMQ
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« Reply #13 on: October 19, 2010, 09:26:09 PM »

N4NYY
  You have the box in front of you, the others don't, so do what YOU think is necessary.
As far as shotgunning goes, I do it all the time, why waste time when you can see problems, shotgun and be done!
 Good luck and have fun!
CMQ
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KD4SBY
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« Reply #14 on: October 22, 2010, 12:12:40 PM »

I got myself an HW-100 and a pwr supply on ebay and the first thing I did was replacing the electrolytics on both of them. They might have been good, but who cares? I have had tube equipment blow up on me because of bad electrolytics, so why take a chance? The replacements were cheap enough.
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