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 Low volume output--Solved

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rich



Join date : 2011-10-01

PostSubject: Low volume output--Solved   2011-10-01, 9:00 pm

Hi guys, i recently purchased a steelman radio/phonograph and i have recapped the unit which got rid of the loud humming. The unit now works but the volume output seems low especially when using the phonograph, the radio seems loud enough when i hit a good station. Any advice would be greatly appreciated.
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Cliff Jones
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Join date : 2010-11-22

PostSubject: Re: Low volume output--Solved   2011-10-02, 12:48 pm

Can you provide a model number? Do you have a schematic?
A coupled of things come to mind, what type of phono cartridge is it, crystal, ceramic, or magnetic? The reason for that question is someone could have replaced the cartridge with the wrong type.
Crystal cartridges can deteriorate over time, I don't know much about ceramic cartridges. If its a magnetic type, they need extra gain, in the form of a preamp.
Turn on the radio and touch each of the phono wires each in turn, with your finger, you should get a very loud buzz from one of them. If not, then a tube would be suspect or faulty wiring. Then go to the volume control but be careful when you touch the volume control as high voltage could be present, (keep the other hand in your pocket so you don't get a shock) The volume control has three wire connectors that look like solder tabs, try touching the center one first, it should have a loud hum or buzz, if it does the the audio section is OK.


Check the wiring connectors to the cartridge, remove and inspect for corrosion, is the other end a RCA or phono jack?
Cold solder joints could be a factor. Check the phono/radio switch for clean and solid contact points.
Check the capacitors around the audio amplifier as they can be open.

As far as reception of radio stations, the signals weaker signals can get lost due to several issues. Some could be caused by a twiddling of RF adjustable components such as capacitor tuning padders, I.F. can screw adjustments, antenna connections or open wires in antenna. The AGC (or AVC) circuit could have problems. and of course the tubes themselves. Some times a blob of solder can short the signal. So check the whole thing for clean and shiny solder joints, also check each tube socket for a firm and clean connection to the tube pins.

This should keep you busy and might solve your problem. Please keep us informed of your progress.

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rich



Join date : 2011-10-01

PostSubject: low volume output   2011-10-03, 8:34 pm

Thanks Cliff for the insight on my problem. The unit i am working on is a 1952 steelman model 517 portable radio phonograph. I have a sams photofact schematic that i have bin referring to and the unit also has a schematic inside it. The cartridge says astatic on it so its magnetic? not 100% sure. The cartridge number matches the one in my photofact so i believe its the proper one for the unit. The phonograph shares the same amplifier as the radio so i dont see any rca or phonojack anywhere. I changed all of the electrolitics and paper caps in the unit one at a time and double checked my work for any errors. One thing i did notice is that when i touch the 50c5 audio tube i get alot of interferance (buzzing). I will try your suggestions Cliff and let you know what i find. Thanks again.
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Cliff Jones
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Join date : 2010-11-22

PostSubject: Re: Low volume output--Solved   2011-10-04, 11:12 am

I unfortunately don't have that schematic.
If the cartridge is magnetic which I would think its not, (because of its age) it would be plastic. If it uses a metal casing and has a screw on the end to hold the needle, it would be a crystal or ceramic cartridge.

Try running your finger across the needle tip while the phono is turned on. If it is weak then the cartridge is suspect. The audio tube sounds good, however there may be a preamp tube just before the output tube, try touching the grid on it to see if you can get a buzz through it. (strong signal is good, weak signal would help pinpoint that to the area that needs attention.)

Sometimes a cap in the amplifier circuit could open, and blocking the audio, also a burned or high resistor value (which may be the case). So check resistors. Make sure the caps that you replaced are good (you can get faulty ones). Connect correctly as to polarity as if you have it in wrong that could be a culprit, because it would pull down the B+ voltage and would effect tube performance.

Sam's usually has voltage check points that you need to check with a voltmeter, if one or more is off then that is a suspect area to start looking at.

Here is a Link for Cartridge repairs and replacements:
>CLICK HERE<

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rich



Join date : 2011-10-01

PostSubject: low volume output   2011-10-18, 7:37 pm

Hello Cliff well after a lot of tinkering i found the problem! It was one of the things you suggested i check, the astatic cartridge is weak. I rigged up another cartridge from another player and it played so loud that the wife started stomping on the floor upstairs! I also replaced all the resistors in the unit for peace of mind. I will contact the website you gave me to see if they can repair my original cartridge. Thanks again Cliff for your advice to this problem. Very Happy
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Cliff Jones
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Join date : 2010-11-22

PostSubject: Re: Low volume output--Solved   2011-10-18, 11:11 pm

Way to go. Glad to Help.

I would encourage you to use your experiences on our forum for assisting those with less experience or Newbies. It will help to further your skills too.

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