• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

When I turn up the Volume, I get a hum.

rolf logan

rolf logan

New Member
I'm restoring an old Magnavox Stereo Console Model 1SC 268F, with a Collaro turntable. Not sure the year, but 60's era for sure.

I've cleaned and lubricated the record changer. I've cleaned the cartridge, put in a new needle, and replaced the tone arm wiring. See Photos.

The changer works well, I can hear the needle working. However, the issue is when I turn the volume to it's lowest setting, all is quiet. As I increase volume, I only get a hum which gets louder as the volume get's louder.

I was told that the problem is in the wiring since there is no hum when the volume is turned to it's very lowest point. Any thoughts?collaro 3.jpeg collaro 2.jpeg collaro 1.jpeg collaro 3.jpeg collaro 2.jpeg collaro 1.jpeg collaro 3.jpeg collaro 2.jpeg collaro 1.jpeg

I would appreciate any suggestions.




collaro 3.jpeg collaro 2.jpeg
 
Register to hide this ad
I have no experience with your turntable but I've recently had a similar issue with my Bogen B-61 turntable. It turns out that the wires inside the headshell were causing most of the hum. Moving them away from each other eliminated most of the hum. My turntable is made to play in either mono or stereo mode. I use it for my mono system. Of the 2 RCA lines coming from it, I only use one for mono. So when I switched to the other RCA line that went to my mono integrated amp, the remainder of the hum disappeared. Totally silent!

Hope this helps.

Gary
 
Yes, in a rebuild of a past Magnavox "Astrosonic", I found the wiring for the headshell to be rather different. It was not really set in a two-channel stereo mode, more like a mono configuration. It was also easy to see one of the leads were not isolated but grounded to signal path not leading to anywhere. I am sure this has to do with the mono vs. stereo mode, which seemed confusing since the console is proposed to be stereo.
If you try the prior poster's guidance, this may eliminate or diminish your hum issue.
 
Make sure both lugs on the cartridge you are using are negative (ground) and make sure everything is common grounded together.

Put that switch back on the turntable. It cuts out the positive left and right when ejecting a record.
 
First, thanks to all for your feedback. Much appreciated. I rewired the tone arm and put the record changer back in the unit and I still have a very loud hum. If I turn the stereo volume down, no hum. I then took the record changer out and put it in another Astrosonic and the record changer played fine. So, all is well with my record changer (Whew), but I still have a hum. I put 3 record changers in this stereo console, I still have a hum on all 3 changers. Any feedback on next steps?
 
Is the original console a tube unit?

Does it have AM & FM? If so, does it hum when in AM or FM mode?
 
Thank you for checking in. It is the original tube unit. Just a record player, no radio. Attached is a photo of the stereo console
 

Attachments

  • Magnavox Model 1SC268F.png
    Magnavox Model 1SC268F.png
    705.6 KB · Views: 30
  • IMG_0010.JPG
    IMG_0010.JPG
    98.3 KB · Views: 29
  • IMG_0009.JPG
    IMG_0009.JPG
    101 KB · Views: 29
Cool!

Does it hum when the volume is turned up without the turntable being connected?

Take a look at the male RCA's that plug into the turntable. Those cheap ass connectors have their grounds soldered to the outer jacks. If they are both broken then you would get hum when turning up the volume. Simple fix of course would be to resolder them. Also, you could run a wire from the chassis of the turntable to the chasssis of the amp. It really does just sound like a ground loop issue. Fingers crossed. :king:
 
Last edited:
Hi Cademan, I visually checked the RCA Male and the solder looked good. I took your suggestion and ran the wire from the Bolt that holds the Chassis to the Record Changer and that worked. You are good, no doubt about it. Thank you. Now, what would be the permanent solution? Do I just run a new ground wire from the Chassis to the Changer and call it a day, or is there a better way?

Also, now that the hum is gone, I do have a new issue - when you turn the volume control and when you don't. Once you set the volume, the volume level goes loud then soft on it's own, up and down with some static in between. I haven't touched any capacitors. I did clean the volume control switch with cleaner, but it may be time to change the capacitors. Your thoughts?
 
Definitely time to change the caps and perhaps some of the carbon resistors, if they're out of spec. Resistors feeding the tube plates are notorious for generating noise when they age.
 
rolf logan said:
Do I just run a new ground wire from the Chassis to the Changer and call it a day, or is there a better way?

Also, now that the hum is gone, I do have a new issue - when you turn the volume control and when you don't. Once you set the volume, the volume level goes loud then soft on it's own, up and down with some static in between.
Click to expand...

You can leave your new wire as is or make it more clean and professional. It's up to you. :thumbsup:

Maybe replace those stock RCA interconnects as one end might have the broken ground which caused your hum.

Also, the volume control just sounds like it needs a very good deox bath or if worse comes to worse, a new volume control.:rockon:
 
Last edited:
rolf logan said:
I'm restoring an old Magnavox Stereo Console Model 1SC 268F, with a Collaro turntable. Not sure the year, but 60's era for sure.
However, the issue is when I turn the volume to it's lowest setting, all is quiet. As I increase volume, I only get a hum which gets louder as the volume get's louder.

I would appreciate any suggestions.
Click to expand...

Increase of hum, hiss, noise when you turn the volume up usually means a noisy gain stage. Could be a tube. Could be a dirty contact of the tube with the socket. Could be a noisy plate resistor.

I'd first try some Deoxit D5 on the tube pins. Tube sockets. Other connectors. Use a little and work it in, by removing and replacing tubes into sockets and connectors several times. See if that helps.

https://www.amazon.com/Hosa-D5S-6-D..._1_5?keywords=deoxit+d5&qid=1637203557&sr=8-5
 
Boochie, you're a little late as he already has all the info he needed to correct the situation. He seems to have had bad RCA's from the turntable to the amp.
 
Hello Mr. Boochie and Cademan,

It's Jan. 29th and I'm still trying to get rid of this hum. I've tried the new wiring and connectors from the turntable to the amp. I've visually checked the RCA connectors from the turntable to the amp, and from the Volume/Treble/Bass assembly to the amp. Both visually check out fine. I've cleaned the tube connectors, and tube sockets on the amp.

I pulled the record changer and tried a different one that works and I still have the hum, only when I put the needle on the record and turn the volume up past half way.

I haven't tested the tubes. It may be worth my while to spend the $70 on new tubes, just to eliminate the tubes as a possible problem. The existing tubes glow orange and are hot to the touch when the amp is fired up.

I really appreciate your previous insights and also, any other insights as to how you would approach resolving this issue.
 
I just cranked the volume up to increase the hum. Then, the record changer proceeded to commence a new cycle and shut off. Maybe too much power caused it to reset?
 
When you say glowing orange, are they glowing from the center or is the outer grey plate structure glowing orange?
 
Thanks for your reply. Much appreciated. IMG_0206.jpg IMG_0207.jpg IMG_0208.jpg IMG_0209.jpg

They glow in the top, middle and bottom. Note attached photos. The rectifier glows on top only. The smallest tube is more faint. The glow at the top is there, but dim. I have edited these photos to enhance the glow
 
Looks okay. From photos looks like filament glow. No glowing anode plates. Have you measured the idle bias on those EL84?

glowing EL84 anode plates (2).jpg
EL84 with glowing plates.
 
You must log in or register to reply here.
Back
Top Bottom