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 Post subject: Need Heathkit AR-15 Electrolytic Substitution Advice
PostPosted: Nov Sat 18, 2017 11:52 pm 
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Joined: Oct Thu 26, 2017 5:04 am
Posts: 5
I'm replacing the electrolytics in a Heathkit AR-15 receiver that was either built by my dad or my uncle. At one point I had three of these receivers, now I think there's only one left. I remember listening to my dad's receiver with a Miracord 50H record player in a custom walnut cabinet he built—good memories!

I'm starting with the power supply board and the power amplifier boards, mostly because I had to partially unwire these boards to pull them up so I could remove the 4000mfd electrolytics on the speaker outputs. I was able to find exact values for almost all of the electrolytics on these boards, except for the 250mfd capacitors, C205 and C207. One of these couples the amplifier stage to the predriver stage. The other is connected to ground and then through a 330ohm resistor to the emitter of the amplifier transistor (see schematic below).

The closest capacitors I was able to find at my local parts store were a 220mfd and a 330mfd. Would either of these significantly change the performance of the amplifier if I used them to replace the existing 250mfd capacitors? Which value would be better to use?

Attachment:
File comment: Schematic
IMG_3429.PNG
IMG_3429.PNG [ 161.9 KiB | Viewed 258 times ]


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 Post subject: Re: Need Heathkit AR-15 Electrolytic Substitution Advice
PostPosted: Nov Sun 19, 2017 5:34 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: New Port Richey, FL, USA
220s are fine. Caps can be off by as much as 20%, so the 250s could have been as low as 225 anyway. And 220 closer than 330.

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