I have recently acquired a mid 50's Decca branded portable turntable and need help rebuilding the single tube amp. My problem is I have a Multiple value filter capacitor that needs replacing, but I don't know how go about with finding a replacement from new parts.
The filter capacitor is made by "Cosmic" and has 3 leads coming out of it/
The values are.....
Red wire +50M. 150W.V.
Blue wire +30M. 150W.V.
Black wire COM. NEG.
Any help with replacing it would be REALLY appriciated!
🙂
The filter capacitor is made by "Cosmic" and has 3 leads coming out of it/
The values are.....
Red wire +50M. 150W.V.
Blue wire +30M. 150W.V.
Black wire COM. NEG.
Any help with replacing it would be REALLY appriciated!
🙂
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Use two separate electrolytic caps, a 50ufd and a 30ufd, with their "-" leads connected together. These days, the size of the two combined will be considerably smaller than the old school dual cap.
Cap value isn't too critical, e.g., a 47u will work for the 50u, a 33u will work for the 30u. Voltage ratings can be higher if that's cheaper/more available. For reliability, use a 105 degree C rated cap.
Cap value isn't too critical, e.g., a 47u will work for the 50u, a 33u will work for the 30u. Voltage ratings can be higher if that's cheaper/more available. For reliability, use a 105 degree C rated cap.
plus, if looks are important you could gut it with a drill (carefully!) and fit both the new caps inside!
WOW thank you "SY" and "costis_n" you rock!! I never thought my question would get answered so quickly! =) I will have more upcoming questions on this player later today when I can get back to working on it.
Also, did you mean 105 Celsius? Operating tempture range? And is that ambient tempture around the cap? Or is it the temp the cap could reach itself internally?
Thanks everyone! 🙂 So just to be clear, the old symbol of "M." means microfarads? And the "150W.V." Means "wave volts" correct?
Also is there anyway I can visually inspect my tube to determine how worn it is? Its crystal clear when i look at it. If it helps its a CBS brand.
Also is there anyway I can visually inspect my tube to determine how worn it is? Its crystal clear when i look at it. If it helps its a CBS brand.
No, you can't test a tube visually (other than obvious trauma or the silvery stuff on the inside of the glass turning white).
Yes, MFD was the old fashioned way of abbreviating "microfarads." WVDC is "working volts DC," or the maximum voltage for which the cap was rated.
Yes, MFD was the old fashioned way of abbreviating "microfarads." WVDC is "working volts DC," or the maximum voltage for which the cap was rated.
The micamold type capacitor is the only other one i need to replace, do these generally go bad? Its rating is .05mfd 400W.V. D.C, how can i test this cap on my multi-meter? And how hard is it to find a replacement cap of the same values? This one is made of mica from what I can gather by what the name on it says.
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Any recommendations on the type of replacement cap i should use for the mica one and how to test the existing one would be greatly appreciated 🙂
ok that's a relief, yeah other then how old it is, the tube, and all the moving parts have almost zero ware, the only reason I decided to rebuild it was the fact that, it made a really loud hum after i turned it on, so I freaked out and turned it off, figuring that it was the Filter Cap lol. Does anyone have nay other recommendations on what I should replace? Those were the only caps in the unit.
Electrolytics and tubes are the "wear" parts here. If this is one of those transformerless deathtraps (i.e., no power transformer, direct connection to mains), I would strongly urge you to get an isolation transformer (for the US, 120V:120V) for safety. A 1 amp rated unit is more than sufficient.
I'm pretty sure this is the power transformer in the second picture
It has
ATC
BA1-UL written on it
Not sure what that means but it defiantly looks like a transformer, and the 1st picture, the big blue component looks like a selenium rectifier.
It says Pyramid 65MA +
Could anyone shed some light if this all seems OK, and if there's anything else that you recommend I replace?
Thanks in advance! Sorry for all the questions haha, you guys ROCK!
It has
ATC
BA1-UL written on it
Not sure what that means but it defiantly looks like a transformer, and the 1st picture, the big blue component looks like a selenium rectifier.
It says Pyramid 65MA +
Could anyone shed some light if this all seems OK, and if there's anything else that you recommend I replace?
Thanks in advance! Sorry for all the questions haha, you guys ROCK!
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That looks like the output transformer.
Trace the power cord- it normally goes through the power switch and then on to the power supply. If it connects to a transformer, you're gold. If it connects to a rectifier, you've got a deathtrap and should get an isolation transformer.
While I'm thinking of it, if the rectifier is selenium, replace it with a standard silicon rectifier. Selenium rectifiers look like a stack of square fins.
Trace the power cord- it normally goes through the power switch and then on to the power supply. If it connects to a transformer, you're gold. If it connects to a rectifier, you've got a deathtrap and should get an isolation transformer.
While I'm thinking of it, if the rectifier is selenium, replace it with a standard silicon rectifier. Selenium rectifiers look like a stack of square fins.
Yes THANK JEABUS!, one lead of the power-cord goes to the volume/power knob and the other to the rectifier. What would be the reason to replace the existing rectifier? and with what silicon one would i replace it with? It appears to be a selenium one with a stack of squares. Did you see it in the pics? Not sure if they showed up in my post.
opps my bad lol it does goto the rectifier, but the lead the goes to the rectifier has the line for the turntable motor soldered to it, so where do I get this transformer and how would I hook it up? Also WHY is this a deathtrap? forgive me for I have made the sin of "not alot" of electrical component knowledge....On this forum lol
You absolutely want to put in an isolation transformer, then. There's lots of threads here about electrical safety, and there's reasons that this type of connection is illegal now. Connect the primary to the line, then the two old power connections from the unit go to the transformer secondary. Easy!
I didn't see the rectifier in the photos (though I didn't look very hard, admittedly), but I worked on enough of this sort of gizmo during my repair shop days in the '60s to have a good suspicion. 😀 Replace the selenium deal with silicon diodes (any general purpose high voltage rectifier like a 1N4007)- how many leads does it have? You'll probably also need to put a 200 ohm (or so) resistor in series with the silicon diode to prevent the voltage from rising too high (silicon diodes have a lower voltage drop than seleniums).
Restoration of old stuff like this is pretty involved, but can be fun and educational.
I didn't see the rectifier in the photos (though I didn't look very hard, admittedly), but I worked on enough of this sort of gizmo during my repair shop days in the '60s to have a good suspicion. 😀 Replace the selenium deal with silicon diodes (any general purpose high voltage rectifier like a 1N4007)- how many leads does it have? You'll probably also need to put a 200 ohm (or so) resistor in series with the silicon diode to prevent the voltage from rising too high (silicon diodes have a lower voltage drop than seleniums).
Restoration of old stuff like this is pretty involved, but can be fun and educational.
The rectifier says Pyramid 65 MA +
Theres Two leads, one on the top and one on the bottom 😀 the gray cord on the power switch is one lead from the outlet plug, and the second connects to the bottom of the rectifier along with the brown cable to the motor, im assuming then that its the negative terminal?
Theres Two leads, one on the top and one on the bottom 😀 the gray cord on the power switch is one lead from the outlet plug, and the second connects to the bottom of the rectifier along with the brown cable to the motor, im assuming then that its the negative terminal?
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