Would anybody out there have a schematic to a Montgomery Wards Model 62-9033 guitar amp ? I don't how the AC line is connected the xformer. It came in my shop showing A dead short . The ac line comes in and the hot lead connects to one side of the power switch . The other side of the switch goes to one of the primarys of the xformer off of the power the switch . The neutral lead goes to fuse and the other lead from fuse goes to other primary lead of the xformer But I'm still seeing a dead short. Please help if anyone can.😀
Looks like you have the AC all figured out as you just described it. If it's showing a dead short (zero ohm) then the transformer is shorted out. However, if you are reading some resistance, then you're probably reading the winding resistance, so the primary might be ok. On most DMMs, people use the "continuity" setting, and presume its a "short". On mine, anything below 30 ohms, the tester beeps. I hope you're actually using the resistance setting.
Good luck.
Good luck.
I don't have the 9033, but you might look through the Airline schematics on the following site, one might be close enough to your model.
Guitar Amplifier Schematics and more
I think Poacher is right, you might just be reading the winding resistance. The primary is usually low resistance.
What exactly does the amp do? You tell us you read a dead short, but is the amp blowing fuses? The real test of the transformer would be to disconnect the secondaries and see if the transformer alone still blows fuses.
Better yet, look up "light bulb limiter" then make one and use it. No more fuse blows.
Guitar Amplifier Schematics and more
I think Poacher is right, you might just be reading the winding resistance. The primary is usually low resistance.
What exactly does the amp do? You tell us you read a dead short, but is the amp blowing fuses? The real test of the transformer would be to disconnect the secondaries and see if the transformer alone still blows fuses.
Better yet, look up "light bulb limiter" then make one and use it. No more fuse blows.
My nephew just brought me that exact same amp for repair. The Montgomery Wards/Airline Model 62-9033. It had a 25 amp fuse in the fuse holder, but may still be OK. I'm just getting started on working on it. I'll let you know if I find a schemo. The power tranny primary measures 6.6 ohms on this one. I haven't applied power yet so I don't know if it's been damaged. All parts appear to be original. I'll test the tubes and replace the PS electrolytic first, and then bring it up on a variac monitoring current draw.
Thanks so much Bob for answering my thread , I hope you find out that your Airline amp is OK. I checked all the tubes and found both of the EL 84s are bad. The 5Y3 rectifier tube is OK as are the 12 AX7s. I still have a direct short somewhere inside this amp. I have a variac but I use my Ballest lamp to check for shorts . I still think I have the AC line hooked up wrong , but it looks right I have the "hot" lead going to one side of the on-off switch and the neutral going to one side of the fuse. Still shows a short.
Hi Poacher thanks for your post. I have a diode test feature on my DMM and I checked the windings and the one set of primaries reads almost 1 ohm. So Tranny may be bad. Secondaries read almost 4 ohms each set . Thanks for all your help.
Hi Enzo . Oh yeah I use a Ballest lamp for sure , it works great , but I think the tranny is bad. Dunno for sure but its reading less than 1 ohm between the primary windings. Thinks for all your help.
One way to tell more accurately, is to put your meter on the lowest resistance setting and short your leads together to see where "zero" is at on your meter. Many times a DMM will be about .2-.3 ohms. Then measure the primary and subtract the "zero" you got before because the meter is already showing .2-.3 ohms for a direct short. This is the true resistance of the winding. But I think Bob's post tells all. There should be at least a few ohms. You have either a partial or complete short. I checked two 18 watt, EL84 amps I have and got 3 and 4 ohms for those primaries.
Is there just one pair of primary leads or do you parallel two windings to get the 120 volt setup?
Also, disconnect the primary from the switch and fuse holder. Then check hooking the test leads to the pri. wires.. You can't discount a shorted power cord where it goes through the chassis if you don't disconnect those primary leads. Depending on how the strain relief is accomplished for the power cord, it could be shorted there. Not too common but worth a check.
Is there just one pair of primary leads or do you parallel two windings to get the 120 volt setup?
Also, disconnect the primary from the switch and fuse holder. Then check hooking the test leads to the pri. wires.. You can't discount a shorted power cord where it goes through the chassis if you don't disconnect those primary leads. Depending on how the strain relief is accomplished for the power cord, it could be shorted there. Not too common but worth a check.
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I'm attaching a schematic of a Supro Model S6424, which appears to be very similar to, if not exactly the same as the model 62-9033 amp circuit we are talking about here. Apparently virtually the same circuit was marketed under several different brand names (Airline, Valco, Mountgommery Ward, Supro ).
The first thing I want to say is that the output tubes look like 6BQ5's and they are not. They are 6973's, which are rare now days. The 6973's were popular in juke boxes and certain early guitar amps (late 50's and early 60's). EH is the only company currently producing the 6973, and the reviews say it's not a good sounding copy, and looks considerably different inside physically. NOS 6973's are going for $50+.
The good news is that the 6CZ5 tube is virtually identical to the 6973, except for one pin connection (pin 8), and although it's not being produced by anyone currently, is available at Antique Electronics in AZ for $9 (apparently a NOS tube), and probably many other places on the web. I haven't actually done the conversion yet and personally seen the results, but it's the screen grid connection that comes out on pins 1 and 8 in the 6973, but only pin 1 on the 6CZ5. Move the screen grid wires to pins one, and it should now be able to use either the 6973, or the 6CZ5, allegedly with no noticable difference of any kind.
The 6BQ5 has a very different pinout, and specs, and the heater draws almost twice the current of these tubes, which could overload the power transformer.
In the one I have, I plan to replace the line cord with a 3 prong for safety reasons. I'll also replace all electrolytics before powering it up. I'll move the screen grid connections to pin one of the output tube sockets, and I had to replace the speaker (coil was rubbing very badly). Hopefully that is all that is wrong with this amp. I'll also replace the 10K resistor in the divider that feeds the secondary grid of the "paraphase" phase splitter with a 20KB pot so I can adjust the drive balance to the output tubes more accurately. Being off a little is arguable a good thing, but if a lot, not good (I'll tweak for perfect balance, since tubes are never perfectly matched at all points on their transfer curve - being off balance by 1dB will bring the even harmonic distortion products up to more naturally match the odd harmonic products).
Jimmy Page allegedly used this amp (or something with virtually the same circuit, tubes and speaker) on the Led Zepplin 1 album, and for part of the Led Zepplin 2 album. My nephew who owns this amp may appreciate that.
The first thing I want to say is that the output tubes look like 6BQ5's and they are not. They are 6973's, which are rare now days. The 6973's were popular in juke boxes and certain early guitar amps (late 50's and early 60's). EH is the only company currently producing the 6973, and the reviews say it's not a good sounding copy, and looks considerably different inside physically. NOS 6973's are going for $50+.
The good news is that the 6CZ5 tube is virtually identical to the 6973, except for one pin connection (pin 8), and although it's not being produced by anyone currently, is available at Antique Electronics in AZ for $9 (apparently a NOS tube), and probably many other places on the web. I haven't actually done the conversion yet and personally seen the results, but it's the screen grid connection that comes out on pins 1 and 8 in the 6973, but only pin 1 on the 6CZ5. Move the screen grid wires to pins one, and it should now be able to use either the 6973, or the 6CZ5, allegedly with no noticable difference of any kind.
The 6BQ5 has a very different pinout, and specs, and the heater draws almost twice the current of these tubes, which could overload the power transformer.
In the one I have, I plan to replace the line cord with a 3 prong for safety reasons. I'll also replace all electrolytics before powering it up. I'll move the screen grid connections to pin one of the output tube sockets, and I had to replace the speaker (coil was rubbing very badly). Hopefully that is all that is wrong with this amp. I'll also replace the 10K resistor in the divider that feeds the secondary grid of the "paraphase" phase splitter with a 20KB pot so I can adjust the drive balance to the output tubes more accurately. Being off a little is arguable a good thing, but if a lot, not good (I'll tweak for perfect balance, since tubes are never perfectly matched at all points on their transfer curve - being off balance by 1dB will bring the even harmonic distortion products up to more naturally match the odd harmonic products).
Jimmy Page allegedly used this amp (or something with virtually the same circuit, tubes and speaker) on the Led Zepplin 1 album, and for part of the Led Zepplin 2 album. My nephew who owns this amp may appreciate that.
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