Tuner Issues w/Zenith H845 - Videokarma.org TV - Video

tlavergne · #1 06-07-2010, 03:39 PM

I have had a Zenith H845 radio. It has been a great radio. Today as I turned the tuning dial the indicator refused to move more than 1/8 of an inch in either direction (both the tuner and the indicator). I feel the same amount of resistance as I turn the dial as I usually do. It worked great last night. So, before I begin tearing into this radio I was looking for some advice for what it might be and how to fix it.
Many thanks.
Tom

marty59 · #2 06-07-2010, 06:14 PM

You're gonna' have to open it up to troubleshoot and it could be more than one thing. What is the condition of the tuning string and is it slipping...is there slack it it?

Provided everything is in place can you freely move the tuning cap by it's pully does everything else moves freely with it? There may be some dry areas that may need a little lube (pivet points, needle slider, etc) but make sure the string is not slipping but should grab..even if there's resistance however stop at this point and determing what is dragging down the works.

Or if there's some slack in it if you press your finger against it and turn the shaft does everything move then? Sometimes you can reposition the dial cord string spring at the tuning cap to take up the slack.

If the string is in good shape then a soap bar rubbed over it does wonders to help make it grip at the tuning shaft.

tlavergne · #3 06-07-2010, 06:25 PM

It feels like it's slipping and not broken. I can still feel resistance when I turn the dial. Thanks for the tips...I'll start tearing it down tomorrow.

Reece · #4 06-07-2010, 09:10 PM

A little oil on the mechanical bearings is good but be sure not to get any lube on the dial string. The string needs to grip the shaft that the knob turns. A good way to do this is to rub some rosin on the part of the string that will be pulled by that shaft. Violin bow rosin would be ideal, but might be hard for a particular individual to come across. Another way is to find a pine tree and take a drip of rosin off of the bark and dissolve it in a little bit of alcohol. Paint the solution on the string and allow to dry.

tlavergne · #5 06-07-2010, 09:34 PM

Rosin eh? Sounds nice and simple. I really think the dial string is slipping and not broken. It looks fairly simple to disassemble to get to the dial string. Hope so.
Thanks for the info.

tlavergne · #6 06-08-2010, 09:10 PM

The dial string is in good shape and I don't think there is excessive slack. It is slipping on a wooden spool that is part of the tuning shaft. I don't have any rosin...soap eh? I would think soap would become a lubricant. Not so apparently.
Many thanks.
Tom

DaveWM · #7 06-08-2010, 09:32 PM

can you get a pic of that wooden part?

marty59 · #8 06-09-2010, 07:46 AM

Bar soap...the wax properties is what will help it to grip. I'm wondering what you mean by "wooden spool" too.

tlavergne · #9 06-09-2010, 07:52 AM

Just behind the face of the radio the shaft goes through a small wooden spool, not unlike a spool used for thread, and then the shaft disappears into the radio. I'll try and post a photo.

tlavergne · #10 06-09-2010, 08:45 AM

If I did this correctly the image should be here.

DaveWM · #11 06-09-2010, 08:52 AM

trying to remember if this one has the cam on the AM vari cap that operates the FM slugs or are the slugs directly tuned by the tuning shaft and the AM vari cap uses a dial string and pulley.

any way I would look for a dial string that has slipped off a small pulley or some other hang up. Since you have it apart now I hope the problem become obvious. Good luck with it. Those are nice sounding radios, I have a couple of that model cabinet. I prefer the older style with the less fussy airplane prop dial.

tlavergne · #12 06-09-2010, 09:19 AM

I don't know a thing about radios, other than I really like them. But it appears to me, as seen in the photo, that the shaft disappears into the chassis and I don't know what it does from there. The dial string from the shaft turns a wheel (the bottom of which is visible in the photo) which spins a shaft that operates these fin like things that engage themselves as you turn the knob. The dial string looks fine. Like I said, I don't know much about old radios but I love the sound of this Zenith. I prefer to listen to this than my Marantz tuner and JBL speakers.

tlavergne · #13 06-09-2010, 01:15 PM

Radio is back together and I am listening to good FM radio once again. Many thanks for the help.
TL

DaveWM · #14 06-09-2010, 01:17 PM

so was it just slipping? glad you got it back together. Yes those old Zeniths were indeed fine radios.

Besides the Y845 I have I use a H615 for AM, another fine old Zenith set.

tlavergne · #15 06-09-2010, 02:49 PM

Yep, slipping. I have a syringe of very fine oil that I used to put a drop or two around. The tuning shaft has bearings...I couldn't believe it. Little ball bearings. I assumed it would have had a brass bushing. The oil helped loosen the moving parts. I put some bees wax on the tuning dial string and the spool. Works great.