ANTIQUE-RADIO-LAB

Antique Radio Forum for Collectors antique-radio-lab.forumotion.com
 
HomeHome  RegisterRegister  FAQFAQ  SearchSearch  Log inLog in  

Share | 
 

 Zenith Model 6-S-128 repairs

View previous topic View next topic Go down 
Go to page : Previous  1, 2, 3
AuthorMessage
kps



Join date : 2016-11-10

PostSubject: Zenith Model 6-S-128 repairs   2016-11-11, 4:16 pm

First topic message reminder :

Hello members!!  I bought my first fixer upper and it plays with a loud hum so I figured I would start to recap it beginning with the wet electrolytic capacitor. I was hoping someone could explain to me how to replace these two 10-10 mfd 450V electrolytic capacitors.  The original 16 mfd 450V wet electrolytic capacitor was left in place for aesthetics but the wires were cut and replaced with one or both of these Mallorys by somebody else. I have a 16 mfd 450V axial Ecap to replace it with.  If anybody could help me with understanding this I would really appreciate it. Also, in the schematic, if you could point out the wires that I labeled in the photo it would really help me to better read and understand the schematic.  Thanks to anyone willing to help!!!!
[You must be registered and logged in to see this link.][You must be registered and logged in to see this image.]
Back to top Go down

AuthorMessage
Cliff Jones
Site Administrator
Site Administrator


Join date : 2010-11-22

PostSubject: Re: Zenith Model 6-S-128 repairs   2016-11-27, 11:59 am

What's wrong with your tube tester? But that's another topic. Let's stick to the radio itself, or we will get confused.
I have asked a couple of the moderators to help out, I should like their experience and expertise at this point. It's always better to have more than one point of view.
Back to top Go down
Cliff Jones
Site Administrator
Site Administrator
avatar

Join date : 2010-11-22

PostSubject: Re: Zenith Model 6-S-128 repairs   2016-11-27, 12:02 pm

Ok take it down to the next step 2ufd. See what you get.
Also take your test leads and short them togather, what does your display show while doing this?

_________________
I'm a Science Thinker, Radio Tinkerer, and all around good guy. Just ask Me!
Back to top Go down
kps



Join date : 2016-11-10

PostSubject: Re: Zenith Model 6-S-128 repairs   2016-11-27, 1:00 pm

Thank you Cliff!!!  Thanks again for your patience and for taking so much to to work with me.
Back to top Go down
Cliff Jones
Site Administrator
Site Administrator
avatar

Join date : 2010-11-22

PostSubject: Re: Zenith Model 6-S-128 repairs   2016-11-27, 1:02 pm

By the way you should have a adapter for measuring capacitors, you meter has a special socket just for capacitors. It's marked something like cX or CX . Two horizontal slots. Regular test leads won't work, unless they have a symbol of capitance on one of test jacks. Doesn't look like yours does, but you should have a small circuit card with a small divider slot and two test leads with tiny alligator clips attached.

If not you can insert the cap leads, one into each slot, the reason for that, if you were using regular test leads, the capacitance between the leads would effect the measurement.
There are some meters that compensate for that, but THIER more expensive.

Go to our topics on test equipment, look for our link on How to use a multimeter
[You must be registered and logged in to see this link.]

this is the best I have found.

_________________
I'm a Science Thinker, Radio Tinkerer, and all around good guy. Just ask Me!
Back to top Go down
kps



Join date : 2016-11-10

PostSubject: Re: Zenith Model 6-S-128 repairs   2016-11-28, 4:42 pm

Thanks Cliff!!!  I tried the Cx slots with two new caps that I had not used in my recap.  Their both radial safety film caps X2 and Y2.  Both are .05 uf.  X2 showed a value of.047 uf and Y2 showed a value of .044.  Should I test the other caps in the radio now Cliff? Not sure if I cut them out that their leads are long enough to get them in Cx.  May have to rig up something.
Back to top Go down
kps



Join date : 2016-11-10

PostSubject: Re: Zenith Model 6-S-128 repairs   2016-11-28, 5:17 pm

The 16 uf Ecap C21 shows a value of 14.0 uf as it sits in the chassis with the negative lead cut. C18 on the speaker field shows a value of .047 uf.
Back to top Go down
Cliff Jones
Site Administrator
Site Administrator
avatar

Join date : 2010-11-22

PostSubject: Re: Zenith Model 6-S-128 repairs   2016-11-28, 7:28 pm

Good readings within tolerance. 
At this point I'm trying to cover so many methods as it comes to mind, they will not be organized.


Any component more than 10% (resistors)to 20% (caps) off of reading is suspect and needs to be replaced.  However capacitors can have quite a leeway if there filter caps in the power supply up to as high as ( - 10% to + 50% depending on manufacture. For paper caps From 20-50%
You can take a chance and only replace the out of tolerance ones. But that's up to you. Or just run the radio.
After you've tested all the paper caps, then you need to concentrate on seeing if there are miswired parts. 
Then Test (resistors including the candohm ones, inductive devices- transformers-both primary and secondaries) speaker voice coil. 

A hint -if the radio no longer starts smoking, then you can approach several methods of further testing.
First one 
Test voltages, even power outlet.
Most older radios were designed to run at 115-117 v.a.c.
Look at a tube manual and see what voltages are expected at the different pins. 
Also note the plate resistance, this will give you an idea of load (resistor) resistance or transformer resistance. Should be close.

_________________
I'm a Science Thinker, Radio Tinkerer, and all around good guy. Just ask Me!
Back to top Go down
Cliff Jones
Site Administrator
Site Administrator
avatar

Join date : 2010-11-22

PostSubject: Re: Zenith Model 6-S-128 repairs   2016-11-28, 8:04 pm

Yes make up your own test jig, for caps.

_________________
I'm a Science Thinker, Radio Tinkerer, and all around good guy. Just ask Me!
Back to top Go down
kps



Join date : 2016-11-10

PostSubject: Re: Zenith Model 6-S-128 repairs   2016-11-28, 9:29 pm

Again thank you Cliff.  Yes I made the test jigs for the Cx scale.  Works perfectly. I tested a couple of the old paper caps left over from my recap and they were fine. I do need to test the R9 and R4 and see where they are. 
Q1.  If the R9 was completely smoked then it would have infinite resistance right? 

Q2.  Would that be enough to lose the sound in the speaker field?
Back to top Go down
Cliff Jones
Site Administrator
Site Administrator
avatar

Join date : 2010-11-22

PostSubject: Re: Zenith Model 6-S-128 repairs   2016-11-28, 10:39 pm

If a resistor were completely smoked, then yes because the physical body would melt away by thermal runaway, or blow up with no further electrical conduction, but in the process of doing this electricity may continue to arc over, causing further damage,  or with less effect to decrease resistance to a lower value.
Yes you need to test them, because of the heat generated, would change resistance.

I sure that when resistance changes it can either allow more or less current than amount designed for in that particular circuit.
That, depending on the resistance that is present, would also change the voltage drop or gain. And limit current through a circuit.
Most resistors are not designed to block a signal, but act as a voltage divider, or to regulate voltage within certain bounds.

You need to test the candohm as that's where the B+ is divided, and because of a short elsewhere  it may have changed also, but a candohm resistor has a metal heat sink that draws away heat to operate as specified, but again excess current can change its resistance.
That's what electronic theory does to help you understand problems and steps to use to repair.
I ask! do you have any background in electronics. The reason I ask is based on the questions you ask.

Understanding this will help me give you support, as I may be explaining things you already know, and therefore giving complicated answers, when not needed.

_________________
I'm a Science Thinker, Radio Tinkerer, and all around good guy. Just ask Me!
Back to top Go down
Cliff Jones
Site Administrator
Site Administrator
avatar

Join date : 2010-11-22

PostSubject: Re: Zenith Model 6-S-128 repairs   2016-11-29, 7:58 am

I am going to rename this topic, so if other people have this model, Internet browsers will find it faster

_________________
I'm a Science Thinker, Radio Tinkerer, and all around good guy. Just ask Me!
Back to top Go down
kps



Join date : 2016-11-10

PostSubject: Re: Zenith Model 6-S-128 repairs   2016-11-29, 8:19 am

Good deal Cliff.  Thank you!!!
Back to top Go down
kps



Join date : 2016-11-10

PostSubject: Re: Zenith Model 6-S-128 repairs   2016-11-29, 9:41 am

Cliff I tested the resistance of both R9 (19k ohms) and R4 (11k ohms).  R9 showed a value of 22.7 set at 200k ohms.  R4 showed a value of 13.5 set at 200k.  These values fall beyond +/- 10%.  I ordered replacements.
Back to top Go down
Cliff Jones
Site Administrator
Site Administrator
avatar

Join date : 2010-11-22

PostSubject: Re: Zenith Model 6-S-128 repairs   2016-11-29, 1:20 pm

So the methods to use:
Before plugging in power. Have a schematic.
 first are as follows, do a smell test for burned components.
 Second do a visual for damage.
Third check for correct tubes and in correct sockets
Fourth test resistors for correct values, may have changed due to age, or recent replacement that isn't correct color code. 
Fifth Check for miss-wiring.
Sixth test inductors and transformers
Seventh test capacitors. Check for polarity.
Eighth test tubes
Ninth look for modifications and restore to original.
Tenth use a variac and dim bulb tester. Bring up slowly increase voltage by 25 volts every 5 minutes and set last voltage at 115-117v.
Eleventh start measuring test point voltages if radio not functioning.
Twelfth do an alignment.

Mark and note all changes. This will help solve similar problems that you run across.

_________________
I'm a Science Thinker, Radio Tinkerer, and all around good guy. Just ask Me!
Back to top Go down
kps



Join date : 2016-11-10

PostSubject: Re: Zenith Model 6-S-128 repairs   2016-11-29, 2:12 pm

OK great!!!  Thanks Cliff!!!!
Back to top Go down
FrankB
Moderator
Moderator
avatar

Join date : 2010-11-22

PostSubject: Re: Zenith Model 6-S-128 repairs   2016-12-01, 4:07 pm

If you disconnect all the transformer secondary wires, and let the transformer "coast" and it gets extremely hot or the dim bulb tester starts glowing a lot, the transformer is shorted. Typically I recommend a half an hr of running.
 his eliminates the transformer as a likely candidate. I have seen internal shorts also, but they are rare.
Back to top Go down
kps



Join date : 2016-11-10

PostSubject: Re: Zenith Model 6-S-128 repairs   2016-12-05, 5:50 pm

O
Hey Cliff and Frank B..........I fixed it!!!  (or......well I had help) I found a local guy through the California Radio Historical Society.  He invited me into his place and schooled me on where I was misreading the schematic.  Long story short, the 2uf Ecap needed to go between R9 and R4 just like the schematic said.....just like you were trying to tell me Cliff. Simply moving that 2uf Ecap solved everything. All systems are go!!! Very strong reception.  Any ideas on an antenna?  I am going to make a 6 ft single lead short long wire to connect to the A terminal.  May go with a doublet.  Your thoughts?  BTW thanks  
for all of your help with this Cliff.  I really appreciate the lessons.




[url=https://servimg.com/view/19571667/37][img][You must be registered and logged in to see this link.]
Back to top Go down
FrankB
Moderator
Moderator
avatar

Join date : 2010-11-22

PostSubject: Re: Zenith Model 6-S-128 repairs   2016-12-30, 4:56 pm

Typically, an antenna of 30-50' is best, along with a good ground.
Great its working!
Back to top Go down
 
Zenith Model 6-S-128 repairs
View previous topic View next topic Back to top 
Page 3 of 3Go to page : Previous  1, 2, 3
 Similar topics
-
» Gledhill PulsacoilIII repairs
» ZENITH 2016 - Part Eight
» Canadian Model Undergoing Big Upgrade (Again)
» GLEDHILL, REPAIRS, PULSACOIL 2000 REPAIRS ENGINEER, BIRMINGHAM. 0121 369 2370
» Model My Diet

Permissions in this forum:You cannot reply to topics in this forum
ANTIQUE-RADIO-LAB :: Radio Repair Bench-
Jump to: