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  #31  
Old 05-14-2016, 06:30 PM
Captainclock Captainclock is offline
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Quote:
Originally Posted by WISCOJIM View Post
Is the hum still there when the volume is all the way down?

.
Yes the hum is there no matter what the volume level is at even when the volume is turned completely down. and like I said whatever is causing the hum noise is also I'm sure causing the unresponsive tuner issue as well.
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  #32  
Old 05-14-2016, 06:32 PM
Captainclock Captainclock is offline
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Quote:
Originally Posted by Ed in Tx View Post
Post 9 jr tech mentioned the rectifiers. My thought too. You checked both of those?
No I didn't check the diodes yet, that was the next thing I was going to check, would I check them with the diode function on my DMM? Also when I go to check the diodes do I need to remove them from the circuit to check them or can they be in circuit yet to check them? Also would a couple 1N4007 diodes work in place of the original diodes if they do turn out to be bad?

Edit: I checked the diodes and here are my results:

Diode 1:
171
118 in reverse

Diode 2:
174
119 in reverse

I measured the diodes with the radio unplugged and turned off, I'm not sure what the numbers mean but maybe some of you guys on here might be able to interpret the results for me as to whether or not my measurements mean the diodes are good or bad, or whether or not I need to have the radio plugged in and powered on to test more accurately, also the diodes were tested using the diode function on my DMM.

Last edited by Captainclock; 05-14-2016 at 06:43 PM.
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  #33  
Old 05-14-2016, 06:56 PM
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jr_tech jr_tech is offline
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Likely you will need to unsolder one end of each diode to get a good test... should read "OL" in one direction and something around 300 to 700 mv in the other direction (depending on the type of diode).

jr
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  #34  
Old 05-14-2016, 07:13 PM
Captainclock Captainclock is offline
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Quote:
Originally Posted by jr_tech View Post
Likely you will need to unsolder one end of each diode to get a good test... should read "OL" in one direction and something around 300 to 700 mv in the other direction (depending on the type of diode).

jr
They are of the "top hat" variety of diodes it says on the diode case 1N2859 on both. They're soldered in rather precariously so I may just cut one of the leads and if they test fine I can just solder them back into place.
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  #35  
Old 05-14-2016, 07:20 PM
Captainclock Captainclock is offline
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Quote:
Originally Posted by jr_tech View Post
Likely you will need to unsolder one end of each diode to get a good test... should read "OL" in one direction and something around 300 to 700 mv in the other direction (depending on the type of diode).

jr
Well I cut one side of each diode out of the circuit and they measured around 600mV for both of them one way and measured "OL" going the other way which means they are working as they should be apparently which means that there must be something else causeing the humming and unresponsive tuner issue besides the diodes.
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  #36  
Old 05-14-2016, 07:41 PM
WISCOJIM WISCOJIM is offline
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Sounds similar to this one: http://audiokarma.org/forums/index.p...mmmmmm.525449/

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  #37  
Old 05-14-2016, 07:54 PM
zeno zeno is offline
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On IC's it may not have used them. They went disco in the
80's IIRC. The way the IF is built I would NOT go
there unless needed.

If the main filter is not the hum check the outputs next
& any transistors direct coupled to them. They will probably get HOT fast.
Its probably the transistors mounted on the chassis in round
holders.

73 Zeno
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  #38  
Old 05-14-2016, 08:04 PM
Captainclock Captainclock is offline
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Quote:
Originally Posted by zeno View Post
On IC's it may not have used them. They went disco in the
80's IIRC. The way the IF is built I would NOT go
there unless needed.

If the main filter is not the hum check the outputs next
& any transistors direct coupled to them. They will probably get HOT fast.
Its probably the transistors mounted on the chassis in round
holders.

73 Zeno
According to a thread on AudioKarma where a guy had a unit that had the same exact issue as mine (where it hummed and no audio minus the blown fuse issue because mine hasn't blown its fuse yet surprisingly enough) they said something about the amplifier's coupling caps being bad which then in turn caused the output transistors to become fried like bacon, and once he replaced the coupling caps on the amplifier board and replaced the output transistors it worked fine for him. I'm hoping that's not what happened with mine because the amplifier board is going to be darn near impossible to remove because for some reason or another the amplifier board's mounting screws are covered in solder so there's no way to unscrew them...

Well I guess I can forget about working on the tuner board specifically on the vernier tuner mechanism because the screws wont budge and the heads keep wanting to strip out on me whenever I try to remove them, which tells me they used poor quality aluminum screws for that part for some reason, which is odd because the rest of the screws they used were stainless steel screws...

Last edited by Captainclock; 05-14-2016 at 10:14 PM.
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  #39  
Old 05-15-2016, 12:56 AM
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Quote:
Originally Posted by Captainclock View Post
According to a thread on AudioKarma where a guy had a unit that had the same exact issue as mine (where it hummed and no audio minus the blown fuse issue because mine hasn't blown its fuse yet surprisingly enough) they said something about the amplifier's coupling caps being bad which then in turn caused the output transistors to become fried like bacon, and once he replaced the coupling caps on the amplifier board and replaced the output transistors it worked fine for him. I'm hoping that's not what happened with mine because the amplifier board is going to be darn near impossible to remove because for some reason or another the amplifier board's mounting screws are covered in solder so there's no way to unscrew them...

Well I guess I can forget about working on the tuner board specifically on the vernier tuner mechanism because the screws wont budge and the heads keep wanting to strip out on me whenever I try to remove them, which tells me they used poor quality aluminum screws for that part for some reason, which is odd because the rest of the screws they used were stainless steel screws...
I'm guessing that the screws that attach the amp board to the heat sink might be filled in with solder to prevent removal... these *should* be left intact. the screws that hold the board/heatsink assembly to the chassis are the ones that need to be removed to remove the amplifier.
Try a better screwdriver on the tuner screws. Do you have any "Liquid Wrench" ?

jr
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  #40  
Old 05-15-2016, 08:51 AM
Captainclock Captainclock is offline
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Quote:
Originally Posted by jr_tech View Post
I'm guessing that the screws that attach the amp board to the heat sink might be filled in with solder to prevent removal... these *should* be left intact. the screws that hold the board/heatsink assembly to the chassis are the ones that need to be removed to remove the amplifier.
Try a better screwdriver on the tuner screws. Do you have any "Liquid Wrench" ?

jr
No I don't have any liquid wrench, and I tried all the screwdrivers I have on the screws and they won't budge without just about stripping out the heads. So I don't know what to say about those screws. although those screws do have a very bad case of cadmium disease as well as a lot of other parts in this unit.
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  #41  
Old 05-15-2016, 11:36 AM
zeno zeno is offline
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Try a drop of WD40 & let it sit a few days. Also heating them
may work. If the heads are stripped you can grab them with
a pair of dikes. Once started they come right out.

For small stuff get a set of ISO phillips heads. The jap stuff
needs a perfect fit or you cant get them out. They let out
a snap then turn OK.

KLH will use the US standard like a #2 phillips.
Buy highest quality so they fit perfect & dont strip like the screws.

73 Zeno
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  #42  
Old 05-15-2016, 01:49 PM
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Electronic M Electronic M is offline
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Quote:
Originally Posted by zeno View Post
Try a drop of WD40 & let it sit a few days. Also heating them
may work. If the heads are stripped you can grab them with
a pair of dikes.
PB Blaster penetrating oil is better than WD-40 at loosening fasteners. If you can grab the head with a vice-grip wrench those are often a bit better at gripping than dikes.
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  #43  
Old 05-15-2016, 05:53 PM
WISCOJIM WISCOJIM is offline
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Or if they are already too messed up, they can be carefully drilled out. I've had to do that many times over the years.

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