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#1 |
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Badcaps Veteran
Join Date: Mar 2006
City & State: Kamloops BC
My Country: Canada
I'm a: Knowledge Seeker
Posts: 2,555
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I found an absolutely ancient GE "transistorized" record player and aside from an unbalanced and excessively cheap pickup arm it has a real bad buzz. It's trying to amplify but more than anything the buzz overwhelms it. The amp circuit itself is very simple. Me being near the needle also seems to change the volume of the buzz indicating a ground loop, I believe.
![]() Black cylinder on the right takes 120v in, there's four transistors, three capacitors and a bunch of resistors. It receives a signal straight from the needle and outputs straight to a speaker. Knobs control power and tone. Never worked with amps before but my assumption is that after 40 years all the caps require replacement, correct?
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Find Nedry! Check the Vending machines!! <----Computer says I need more beer.
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#2 |
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Badcaps Veteran
Join Date: Feb 2010
City & State: S.F. Bay area
My Country: USA
Line Voltage: 120V 60Hz
I'm a: Knowledge Seeker
Posts: 7,225
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Have not work on one of these since the very early 70's. I thing it get the low voltage AC from the motor winding otherwise you will see big resistor to drop the 120Vac to about 12V. That large cap sitting between the two pots is the DC filter cap. The little black transistor sitting between the two push-pull out put transistors ( with heat sink on them) is for phase splitter/driver for the push-pull output section. The second medium size electrolytic cap is the DC blocker for the out put circuits to the speaker. The smallest electrolytic cap on the left is the input cap from for the phase splitter transistor. The small ceramic disk on the top left by the tone control pot is for the tone control circuits.
Yes, recap first. This amp may use Germanium transistors which has very high leakage which can cause a lot of problem such as low gain and draws a lot of current.
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Never stop learning Baisc LCD TV and Monitor troubleshooting guides. http://www.badcaps.net/forum/showthr...956#post305956 Voltage Regulator (LDO) testing: http://www.badcaps.net/forum/showthr...999#post300999 Inverter testing using old CFL: http://www.badcaps.net/forum/showthr...er+testing+cfl Tear down pictures : Hit the ">" Show Albums and stories" on the left side http://s807.photobucket.com/user/budm/library/ TV Factory reset codes listing: http://www.badcaps.net/forum/showthread.php?t=24809 Last edited by budm; 05-19-2012 at 10:36 PM.. |
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#3 |
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"What problem?"
Join Date: Jan 2011
City & State: Reading, PA
My Country: USA
Line Voltage: 120/240V, 60Hz, 1ph
I'm a: Professional Tech
Posts: 591
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And one side of the AC line goes right to that board- hot chassis. Look at the insulated pot shafts.
Check the carbon comps- they can drift upwards in value.
__________________
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