Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Oct Wed 23, 2019 7:00 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 21 posts ]  Go to page 1, 2  Next
Author Message
 Post subject: Fanon Masco FMA-20
PostPosted: Aug Wed 15, 2018 6:29 am 
New Member

Joined: Aug Wed 15, 2018 6:10 am
Posts: 9
Hello, I am new to the vintage amp scene so please forgive me for lacking knowledge. Anyway, I was going through a passed relatives house and spotted this amp tucked away. I got it home, disassembled and cleaned up and everything appears to be in great shape. Now I know some of the old components probably need to be replaced, but in my haste I overlooked that and the fact that its rated for 117 volt power and plugged it in and turned it on for about 5 seconds. Just enough to ensure it did function somewhat. Although I didnt touch the case since there is no 3rd pin.

So my questions, I'm quite lost here. Is it bad to run it on my standard 120v sockets? Is there a way to convert it to run on 120v? (I remember seeing someone do this with another) Can someone please tell me the microphone and speaker connection types? I've looked at many connectors and cannot find a match. And anyone who could point me toward documentation like a manual or schematic would be greatly appreciated. Some sort of operation manual would be great. Oh and one last thing, I know it's a good idea to replace some of the old components, but I'm not sure what. Although all of them look good and I suspect this amp was used little.


Top
 Profile  
 
 Post subject: Re: Fanon Masco FMA-20
PostPosted: Aug Fri 17, 2018 7:20 pm 
Member
User avatar

Joined: Jan Tue 23, 2007 10:23 pm
Posts: 5378
Location: Chicago IL
117 vs 120 is too small of a difference and it doesn't matter. A search online should render a manual somewhere. What happened when you plugged it in?

_________________
-Carlos


Top
 Profile  
 
 Post subject: Re: Fanon Masco FMA-20
PostPosted: Aug Fri 17, 2018 7:40 pm 
New Member

Joined: Aug Wed 15, 2018 6:10 am
Posts: 9
tube42 wrote:
117 vs 120 is too small of a difference and it doesn't matter. A search online should render a manual somewhere. What happened when you plugged it in?


Just making sure. I remember some guys elsewhere using a variac to get 120v on a 115v outlet and someone else wiring up his amp different to account for the change in voltage. Anyway, I only had it on for 5 seconds but I could hear the transformers hum and the tubes began to warm up. Nothing out of the ordinary I dont think

Edit: kept it on for a little longer and the 6ca4 tube (according to the tube layout diagram) begins making strange popping noises and flashes of light can be seen inside the tube. I'm guessing a bad tube? Or maybe from having no load on it? I didn't keep it on for long after that started, trust me. Oh and the transformer could be heard making a louder hum along with the pops of the tube.


Top
 Profile  
 
 Post subject: Re: Fanon Masco FMA-20
PostPosted: Aug Fri 17, 2018 10:40 pm 
Member
User avatar

Joined: Jan Tue 23, 2007 10:23 pm
Posts: 5378
Location: Chicago IL
Yikes. Don't power that thing up anymore. Sounds like the tube has a short. The hum may be due to a large current draw. It needs to be serviced. I wouldn't trust just a change of tube.

_________________
-Carlos


Top
 Profile  
 
 Post subject: Re: Fanon Masco FMA-20
PostPosted: Aug Sat 18, 2018 12:24 am 
Member
User avatar

Joined: Sep Mon 16, 2013 2:42 am
Posts: 3484
Location: Tucson, Arizona U.S.A.
And don't turn it on without a load. That can cause damage even if everything is in good shape.

As to the connectors, post pictures.

_________________
Jim Mueller


Top
 Profile  
 
 Post subject: Re: Fanon Masco FMA-20
PostPosted: Aug Sat 18, 2018 6:05 am 
New Member

Joined: Aug Wed 15, 2018 6:10 am
Posts: 9
I might try and find the short later. I have a multimeter, soldering tools, etc but these old amps are fairly new to me.

Here are the connectors. I'll probably look like I know nothing at all even more but I cant find them. I actually dont know the speaker or mic connectors.
Image


Top
 Profile  
 
 Post subject: Re: Fanon Masco FMA-20
PostPosted: Aug Sat 18, 2018 6:47 am 
Member
User avatar

Joined: Jan Tue 23, 2007 10:23 pm
Posts: 5378
Location: Chicago IL
Center ones are just RCAs, one on the right is an old timey coaxial mic connector. Im sure someone knows the real name. The speaker conector is also an old time thing that is long forgotten. I guess that wasnt much help. :lol: You can defo get them.

_________________
-Carlos


Top
 Profile  
 
 Post subject: Re: Fanon Masco FMA-20
PostPosted: Aug Sat 18, 2018 6:50 am 
New Member

Joined: Aug Wed 15, 2018 6:10 am
Posts: 9
Haha, thanks anyway. I have a manual on the way so maybe it can shed some light


Top
 Profile  
 
 Post subject: Re: Fanon Masco FMA-20
PostPosted: Aug Sat 18, 2018 7:39 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 6509
Location: Black Hills, SD 57745
A peek at the rear of the speaker would show which pins were used. One should be a ground/common. If more than two, might be for different speaker impedances or perhaps even a 70-volt output, which would require a transformer on the speaker itself. That's used for long wiring runs or multiple speakers in different locations. Otherwise, you should see the 4/8/or 16 ohm output, which would come from an output transformer on the amp's chassis. The manual should help sort that out.

Lacking a proper connector, you can insert a rod or screw that fits into the sockets and solder or clip your speaker wires to that. Slip a tube or heat shrink over them or tape 'em to keep them from touching one another. You could also skip the pin idea and just solder wires directly to the terminals on the rear. Not as elegant as the correct plug, but it'll work till you locate one.

The mic is an Amphenol connector. I have several from my dad's old parts stash. Also used on some vintage test probes. There's probably adapters to convert it to a more modern mic connector or your own available connector could be soldered on to the rear, like with the speaker, just using a short shielded cable for the hookup.

Besides a sparking tube, expect to find a shorted cap(s) or other failed parts. The transformer will likely fail if testing continues without finding/replacing what's gone bad.

-Ed

_________________
My life is loosely based on a true story.


Top
 Profile  
 
 Post subject: Re: Fanon Masco FMA-20
PostPosted: Aug Sat 18, 2018 8:23 pm 
New Member

Joined: Aug Wed 15, 2018 6:10 am
Posts: 9
Good info, not home at the moment but I remember it being 3 wires. I think one went to a screw that is used to select the impedance of the speaker, one for postive voltage, and one for ground. I think
But I'm not sure where all three wires would go on a speaker. The impedance selection screw selects a different wire from the transformer. Maybe the other wire that I said is postive, isn't what I think it is. Haven't traced it that far yet. Not sure really, haven't really seen too many 3 wire speakers. Unless it's related to XLR?

Any good tips for finding the short?


Top
 Profile  
 
 Post subject: Re: Fanon Masco FMA-20
PostPosted: Aug Sat 18, 2018 11:07 pm 
Member
User avatar

Joined: Nov Sat 07, 2009 11:37 pm
Posts: 2184
Location: Sayreville, NJ 08872
BreadLord wrote:
Haha, thanks anyway. I have a manual on the way so maybe it can shed some light

It's on the way. Be there Tuesday.

_________________
Pete, WA2CWA - "A cluttered desk is a sign of genius"
http://www.classicradiomanuals.com


Top
 Profile  
 
 Post subject: Re: Fanon Masco FMA-20
PostPosted: Aug Sat 18, 2018 11:45 pm 
New Member

Joined: Aug Wed 15, 2018 6:10 am
Posts: 9
manualman wrote:
BreadLord wrote:
Haha, thanks anyway. I have a manual on the way so maybe it can shed some light

It's on the way. Be there Tuesday.


Thank you!


Top
 Profile  
 
 Post subject: Re: Fanon Masco FMA-20
PostPosted: Aug Sun 19, 2018 4:13 am 
New Member

Joined: Aug Wed 15, 2018 6:10 am
Posts: 9
Update: I was very very wrong :lol:
Okay so there are 2 speaker connections. One labeled 70 volts and one not.
On the non 70 volt connection, it has a ground wire and has the impedance selection wire that picks different wires of the transformer.
On the 70 volt connection, it has ground, shares the same impedance selector, and has a 3rd wire from the transformer.
So if I figure out this popping/short I could test it.


Top
 Profile  
 
 Post subject: Re: Fanon Masco FMA-20
PostPosted: Aug Mon 20, 2018 7:53 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 4270
Location: Boston, MA USA
Don't worry about lack of a speaker load -- with no signal it won't matter, and you are very far away from that. The sparking in the rectifier tube is destructive and needs to be fixed before you do anything else. First you must replace all electrolytic capacitors and any paper capacitors in the unit, as well as the 6CA4 tube which is now ruined. Most likely you have a shorted electrolytic filter capacitor which destroyed the 6CA4.

Before ordering any parts try this: remove the 6CA4 and power up the amplifier. The rest of the tubes should light up. Listen carefully to the power transformer. If if hums loudly or makes any popping sounds don't go any further.

-David


Top
 Profile  
 
 Post subject: Re: Fanon Masco FMA-20
PostPosted: Aug Mon 20, 2018 11:10 pm 
Member
User avatar

Joined: Sep Mon 16, 2013 2:42 am
Posts: 3484
Location: Tucson, Arizona U.S.A.
Quote:
Don't worry about lack of a speaker load -- with no signal it won't matter

How do you know there isn't a signal? The thing isn't working properly yet. There could be hum, intermittent shorts, or a slip of a test probe could introduce an unintended signal. Always have a load, or at least short the output (applies only to tube amplifiers, solid state units have other considerations depending on the circuit they use). Shorting the output is only for the most basic tests like DC voltage levels. It will mess up any AC tests of the output stage or places where the output is included in a feedback loop. For those tests a real load is needed.

_________________
Jim Mueller


Top
 Profile  
 
 Post subject: Re: Fanon Masco FMA-20
PostPosted: Aug Tue 21, 2018 1:23 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 4270
Location: Boston, MA USA
It's a good idea to have a load. Also a good idea to leave the volume control turned down. But highly premature in this case -- there is a HUGE DC problem to sort out so no need to worry about AC testing. Certainly a load is irrelevant for the power transformer test with rectifier tube removed.

-David


Top
 Profile  
 
 Post subject: Re: Fanon Masco FMA-20
PostPosted: Aug Tue 21, 2018 1:33 am 
New Member

Joined: Aug Wed 15, 2018 6:10 am
Posts: 9
Without the 6CA4 the amp is a lot quieter with a very faint transformer hum. The 7189 tubes do appear to function.

I have not had time to test components, sorry


Top
 Profile  
 
 Post subject: Re: Fanon Masco FMA-20
PostPosted: Aug Wed 22, 2018 1:01 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 4270
Location: Boston, MA USA
Good news! Order your electrolytic capacitors and a new 6CA4. There may also be tubular capacitors which need replacement, or they may be film or disk types which will be fine. No more power until this is done.

-David


Top
 Profile  
 
 Post subject: Re: Fanon Masco FMA-20
PostPosted: Aug Wed 22, 2018 2:06 am 
Member

Joined: Sep Thu 23, 2010 6:37 am
Posts: 11716
Location: Powell River BC Canada
Here are specs.

25 watts peak power output music waveform rating


:D

Attachment:
Fanon Masco  FMA 20   1965.jpg
Fanon Masco FMA 20 1965.jpg [ 57.26 KiB | Viewed 1488 times ]

_________________
de
VE7ASO VE7ZSO
Amateur Radio Literacy Club. May we help you read better.
Steve Dow
ve7aso@rac.ca


Top
 Profile  
 
 Post subject: Re: Fanon Masco FMA-20
PostPosted: Aug Wed 22, 2018 5:08 pm 
New Member

Joined: Aug Wed 15, 2018 6:10 am
Posts: 9
I have not had time, but in the next few days I will be ordering parts. Possibly this weekend.
Thanks for all the help you guys
I'll keep you updated


Top
 Profile  
 
Post New Topic Post Reply  [ 21 posts ]  Go to page 1, 2  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: Scott and 3 guests



Search for:
Jump to:  




























Privacy Policy :: Powered by phpBB