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 Post subject: Re: Zenith Y960 amp removal help?
PostPosted: Sep Tue 15, 2020 2:21 am 
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Joined: Sep Thu 20, 2007 3:16 am
Posts: 1007
Location: Winter Park, Florida
I have two of these consoles and they are both dead quiet, no hum or hiss of any kind.

That pad on the back panel and in the speaker enclosures is not asbestos, it is an acoustic absorbing material for the speaker system.


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 Post subject: Re: Zenith Y960 amp removal help?
PostPosted: Sep Tue 15, 2020 7:52 am 
Member

Joined: Apr Sun 16, 2017 7:57 pm
Posts: 274
orthophonic wrote:
I have two of these consoles and they are both dead quiet, no hum or hiss of any kind.

That pad on the back panel and in the speaker enclosures is not asbestos, it is an acoustic absorbing material for the speaker system.


Hi Orthophonic,

Good to know. If you listen via headphones (with no music playing) on tape and phono, do you hear any hum or inordinate hissing?


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 Post subject: Re: Zenith Y960 amp removal help?
PostPosted: Sep Tue 15, 2020 3:31 pm 
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Joined: Feb Wed 04, 2015 12:26 am
Posts: 1288
zenithconsole wrote:
If you plug headphones in and rotate volume control back and forth, do you hear a strange hiss in addition to the hum?

Can you post a recording of the noise?

Mine has hiss and hum.


The hiss is caused by leaky germanium transistors.


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 Post subject: Re: Zenith Y960 amp removal help?
PostPosted: Sep Tue 15, 2020 6:29 pm 
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Joined: Apr Sun 16, 2017 7:57 pm
Posts: 274
Can the 10K resistors in the tuner / preamp cause hiss?


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 Post subject: Re: Zenith Y960 amp removal help?
PostPosted: Sep Wed 16, 2020 2:52 am 
Member

Joined: Feb Wed 04, 2015 12:26 am
Posts: 1288
zenithconsole wrote:
Can the 10K resistors in the tuner / preamp cause hiss?


Hiss is caused by active devices such as tube or transistor. Resistor is passive.


Germanium hiss

https://www.youtube.com/watch?v=t6hEnAx1YR8


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 Post subject: Re: Zenith Y960 amp removal help?
PostPosted: Sep Wed 16, 2020 5:00 am 
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Joined: Apr Sun 16, 2017 7:57 pm
Posts: 274
The hiss patterns are different in the left and right channel.

I swapped all the left channel transistors with the right channel and the hiss patterns did not move to the opposite channel.

Could higher value carbon comp resistors in the tuner/preamp be going bad?


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 Post subject: Re: Zenith Y960 amp removal help?
PostPosted: Sep Wed 16, 2020 12:53 pm 
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Joined: Feb Wed 04, 2015 12:26 am
Posts: 1288
zenithconsole wrote:
The hiss patterns are different in the left and right channel.

I swapped all the left channel transistors with the right channel and the hiss patterns did not move to the opposite channel.

Could higher value carbon comp resistors in the tuner/preamp be going bad?


all that means is the problem is further up the signal chain. I'm going to be very clear on this, this is not fixable without equipment such as an oscilloscope. Resistors do not cause hiss. Leaky capacitors might, but its highly unlikely.
Especially if it does this on all inputs. You have bad transistors and this is a very complicated problem. If you are inexperienced, it will have to be serviced by a professional.


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 Post subject: Re: Zenith Y960 amp removal help?
PostPosted: Sep Wed 16, 2020 9:49 pm 
New Member

Joined: Aug Sun 23, 2020 5:44 am
Posts: 15
Artcurus wrote:
zenithconsole wrote:
The hiss patterns are different in the left and right channel.

I swapped all the left channel transistors with the right channel and the hiss patterns did not move to the opposite channel.

Could higher value carbon comp resistors in the tuner/preamp be going bad?


all that means is the problem is further up the signal chain. I'm going to be very clear on this, this is not fixable without equipment such as an oscilloscope. Resistors do not cause hiss. Leaky capacitors might, but its highly unlikely.
Especially if it does this on all inputs. You have bad transistors and this is a very complicated problem. If you are inexperienced, it will have to be serviced by a professional.


any ideas on what could be causing a 60hz hum across all channels that varies with volume and is worst via the Tape IN setting? Further, the metal surfaces on the console (buttons, turntable, headphone jack) are all warm/electrified to the touch! i have it unplugged and am scheduled to have a professional tech look at it this weekend.

amp is recapped, see photos. my tuner has not been recapped yet but i have a very similar hum to zenithconsole and what feels like a bad ground somewhere.


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 Post subject: Re: Zenith Y960 amp removal help?
PostPosted: Sep Wed 16, 2020 10:28 pm 
Member

Joined: Feb Wed 04, 2015 12:26 am
Posts: 1288
Brettzky99 wrote:
Artcurus wrote:
zenithconsole wrote:
The hiss patterns are different in the left and right channel.

I swapped all the left channel transistors with the right channel and the hiss patterns did not move to the opposite channel.

Could higher value carbon comp resistors in the tuner/preamp be going bad?


all that means is the problem is further up the signal chain. I'm going to be very clear on this, this is not fixable without equipment such as an oscilloscope. Resistors do not cause hiss. Leaky capacitors might, but its highly unlikely.
Especially if it does this on all inputs. You have bad transistors and this is a very complicated problem. If you are inexperienced, it will have to be serviced by a professional.


any ideas on what could be causing a 60hz hum across all channels that varies with volume and is worst via the Tape IN setting? Further, the metal surfaces on the console (buttons, turntable, headphone jack) are all warm/electrified to the touch! i have it unplugged and am scheduled to have a professional tech look at it this weekend.

amp is recapped, see photos. my tuner has not been recapped yet but i have a very similar hum to zenithconsole and what feels like a bad ground somewhere.


Replace the .1 cap still left first.

Go back through and verify each connection. You can also take a wire and go from chassis of the amp, to the chassis of the tuner, and see if the hum goes away. You are correct, you have a loose ground or a miswire.


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 Post subject: Re: Zenith Y960 amp removal help?
PostPosted: Sep Wed 16, 2020 10:41 pm 
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Joined: Aug Sun 23, 2020 5:44 am
Posts: 15
thanks, FYI it hummed like this before the recap and got 20-30% better after the recap

to confirm you mean the a small round ceramic disc capacitor connected from one of the fuse holder terminals to ground, correct?


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 Post subject: Re: Zenith Y960 amp removal help?
PostPosted: Sep Wed 16, 2020 11:54 pm 
Member

Joined: Feb Wed 04, 2015 12:26 am
Posts: 1288
Brettzky99 wrote:
thanks, FYI it hummed like this before the recap and got 20-30% better after the recap

to confirm you mean the a small round ceramic disc capacitor connected from one of the fuse holder terminals to ground, correct?



The brown capacitor at the bottom left side of the chassis in the pic.

Mouser part number

https://www.mouser.com/ProductDetail/Vi ... lxRA%3D%3D


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 Post subject: Re: Zenith Y960 amp removal help?
PostPosted: Sep Thu 17, 2020 12:16 am 
Member

Joined: Apr Sun 16, 2017 7:57 pm
Posts: 274
Artcurus wrote:
Brettzky99 wrote:
thanks, FYI it hummed like this before the recap and got 20-30% better after the recap

to confirm you mean the a small round ceramic disc capacitor connected from one of the fuse holder terminals to ground, correct?



The brown capacitor at the bottom left side of the chassis in the pic.

Mouser part number

https://www.mouser.com/ProductDetail/Vi ... lxRA%3D%3D


Hi Artcurus,

Can you walk me through why this cap (C143) is suspect in your view and should be replaced? 0.1uF 400V Good-All. Is this a Mylar (polyester)?

Unless I'm mistaken, C143 appears to be an arc suppression capacitor to prevent a "thump" being sent to the speakers when the record changer is turned on or off. One end of this cap is tied to the record changer plug.

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Attachment:
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 Post subject: Re: Zenith Y960 amp removal help?
PostPosted: Sep Thu 17, 2020 3:07 am 
Member

Joined: Feb Wed 04, 2015 12:26 am
Posts: 1288
zenithconsole wrote:
Artcurus wrote:
Brettzky99 wrote:
thanks, FYI it hummed like this before the recap and got 20-30% better after the recap

to confirm you mean the a small round ceramic disc capacitor connected from one of the fuse holder terminals to ground, correct?



The brown capacitor at the bottom left side of the chassis in the pic.

Mouser part number

https://www.mouser.com/ProductDetail/Vi ... lxRA%3D%3D


Hi Artcurus,

Can you walk me through why this cap (C143) is suspect in your view and should be replaced? 0.1uF 400V Good-All. Is this a Mylar (polyester)?

Unless I'm mistaken, C143 appears to be an arc suppression capacitor to prevent a "thump" being sent to the speakers when the record changer is turned on or off. One end of this cap is tied to the record changer plug.

Attachment:
amp.jpg


Attachment:
c143.jpg


Attachment:
arc.jpg



Good-All are terrible, they are really a paper cap in a plastic case.. The cap can short or become leaky and send whatever voltages on the cap to ground. I had one in my Sherwood S5500II that was in the preamp section. It had been left from a previous tech. It shorted out and took a 12AX7 with it.

Old caps in these systems are not worth it and 50-60 year old caps in early SS, are starting to fail. Same with equipment dating to the early 70's.

Mylar caps are rare in typical mid grade consumer systems such as this. They start showing up in higher quality equipment such as Fischer.

The only other place they *might* show up is in tuners.


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 Post subject: Re: Zenith Y960 amp removal help?
PostPosted: Sep Thu 17, 2020 3:18 am 
Member

Joined: Feb Wed 04, 2015 12:26 am
Posts: 1288
Brettzky99 wrote:
Artcurus wrote:
zenithconsole wrote:
The hiss patterns are different in the left and right channel.

I swapped all the left channel transistors with the right channel and the hiss patterns did not move to the opposite channel.

Could higher value carbon comp resistors in the tuner/preamp be going bad?


all that means is the problem is further up the signal chain. I'm going to be very clear on this, this is not fixable without equipment such as an oscilloscope. Resistors do not cause hiss. Leaky capacitors might, but its highly unlikely.
Especially if it does this on all inputs. You have bad transistors and this is a very complicated problem. If you are inexperienced, it will have to be serviced by a professional.


any ideas on what could be causing a 60hz hum across all channels that varies with volume and is worst via the Tape IN setting? Further, the metal surfaces on the console (buttons, turntable, headphone jack) are all warm/electrified to the touch! i have it unplugged and am scheduled to have a professional tech look at it this weekend.

amp is recapped, see photos. my tuner has not been recapped yet but i have a very similar hum to zenithconsole and what feels like a bad ground somewhere.



Brettzky,

That's a 400 volt cap, not 100 volt. The picture wasn't clear.


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 Post subject: Re: Zenith Y960 amp removal help?
PostPosted: Sep Thu 17, 2020 4:52 am 
Member

Joined: Apr Sun 16, 2017 7:57 pm
Posts: 274
Artcurus wrote:
Good-All are terrible, they are really a paper cap in a plastic case.. The cap can short or become leaky and send whatever voltages on the cap to ground. I had one in my Sherwood S5500II that was in the preamp section. It had been left from a previous tech. It shorted out and took a 12AX7 with it.

Old caps in these systems are not worth it and 50-60 year old caps in early SS, are starting to fail. Same with equipment dating to the early 70's.

Mylar caps are rare in typical mid grade consumer systems such as this. They start showing up in higher quality equipment such as Fischer.

The only other place they *might* show up is in tuners.


Was the Good-All cap that shorted in your Sherwood in this same brown plastic package?

It appears this Good-All package was an early implementation of Mylar introduced to market circa 1955.

Saul Marantz utilized these brown Good-Alls for the legendary Marantz 8B tube amplifier, and his products were not designed to a price point.

The Zenith Y960 tuner/preamp chassis also utilizes several of the Good-Alls.

Of course, the Marantz wire management is a bit better than the Zenith rat's nest! :D

Found this image of the 8B online, containing 8 Good-All capacitors.

Attachment:
1527512-ffdd9b53-marantz-8b-tube-power-amp.jpg
1527512-ffdd9b53-marantz-8b-tube-power-amp.jpg [ 703.27 KiB | Viewed 132 times ]


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 Post subject: Re: Zenith Y960 amp removal help?
PostPosted: Sep Thu 17, 2020 1:15 pm 
Member

Joined: Feb Wed 04, 2015 12:26 am
Posts: 1288
zenithconsole wrote:
Artcurus wrote:
Good-All are terrible, they are really a paper cap in a plastic case.. The cap can short or become leaky and send whatever voltages on the cap to ground. I had one in my Sherwood S5500II that was in the preamp section. It had been left from a previous tech. It shorted out and took a 12AX7 with it.

Old caps in these systems are not worth it and 50-60 year old caps in early SS, are starting to fail. Same with equipment dating to the early 70's.

Mylar caps are rare in typical mid grade consumer systems such as this. They start showing up in higher quality equipment such as Fischer.

The only other place they *might* show up is in tuners.


Was the Good-All cap that shorted in your Sherwood in this same brown plastic package?

It appears this Good-All package was an early implementation of Mylar introduced to market circa 1955.

Saul Marantz utilized these brown Good-Alls for the legendary Marantz 8B tube amplifier, and his products were not designed to a price point.

The Zenith Y960 tuner/preamp chassis also utilizes several of the Good-Alls.

Of course, the Marantz wire management is a bit better than the Zenith rat's nest! :D

Found this image of the 8B online, containing 8 Good-All capacitors.

Attachment:
1527512-ffdd9b53-marantz-8b-tube-power-amp.jpg



The bigger problem on that one is that cracked bumblebee cap.

Here's the thread on Good All.

viewtopic.php?p=1984972

The cap that shorted out on mine was brown.


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 Post subject: Re: Zenith Y960 amp removal help?
PostPosted: Sep Thu 17, 2020 1:17 pm 
Member

Joined: Feb Wed 04, 2015 12:26 am
Posts: 1288
Brettzky99 wrote:
thanks, FYI it hummed like this before the recap and got 20-30% better after the recap

to confirm you mean the a small round ceramic disc capacitor connected from one of the fuse holder terminals to ground, correct?

Brettzky,

Make sure the tech puts a polarized plug on this unit.


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 Post subject: Re: Zenith Y960 amp removal help?
PostPosted: Sep Thu 17, 2020 5:57 pm 
Member

Joined: Apr Sun 16, 2017 7:57 pm
Posts: 274
Hi Artcurus,

Found this post which pertains to the brown (probably more of a maroon color) Good-All with a 1967 manufacture code used in the Zenith.

viewtopic.php?f=6&t=341227

Tom Albrecht wrote:
I also agree that if your Good-All caps turn out to be Mylar, they don't need to be replaced. As a very rough guide:

- If your amp was made before 1960, the tubular caps are paper, and should be replaced
- If your amp was made between 1960 and 1965, the caps could be either paper or polymer dielectric, so testing for leakage would be a good step before replacing
- If your amp was made after 1965, the caps are likely polymer dielectric, and usually are still good

Note the the appearance of the case alone usually doesn't tell you whether the dielectric inside is paper or polymer. There are lots of paper dielectric capacitors in molded plastic cases that need to be replaced. As noted above, however, Good-All caps with maroon molded plastic cases probably are Mylar. Earlier Good-All caps with pink or light green molded plastic are likely to be paper dielectric.


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 Post subject: Re: Zenith Y960 amp removal help?
PostPosted: Sep Sat 19, 2020 5:06 am 
Member

Joined: Apr Sun 16, 2017 7:57 pm
Posts: 274
If C146 (across the two rectifier diodes) is bad, could it cause hum? If not, are there any other caps on the power amp schematic below that could create a ground fault hum if they fail?

Attachment:
poweramp.jpg
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Attachment:
amp.jpg
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 Post subject: Re: Zenith Y960 amp removal help?
PostPosted: Sep Sat 19, 2020 5:23 am 
Member

Joined: Apr Sun 16, 2017 7:57 pm
Posts: 274
orthophonic wrote:
I have two of these consoles and they are both dead quiet, no hum or hiss of any kind.

That pad on the back panel and in the speaker enclosures is not asbestos, it is an acoustic absorbing material for the speaker system.


Have you listened on headphones? Did you change the germaniums on the amp chassis to silicon and rebias? Or are you still using the original germaniums on the amp chassis?


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