Garage Hoopty

[Hydrolastic]

The 2st208 garage console gave out. The amp 175 just could not drive the CG woofers! It did for almost a year but a couple of days ago the fuse blew and then no sound after that. Suspect the transformer it will get fixed but not now.
Inspired by the Frankengrand I thought about what I really wanted from a garage console, It needs horns and big woofers and a more powerful amp! Got to looking at what I had left over from other projects. I have the beat up imperial console case and its speakers and horns. I also want to install it under the workbench so front facing controls would be good. The extra recapped AMP 182 BA chassis and the extra 54-01 preamp/tuner left over from the Continental project. All of the pieces could go together I think? Covering early 58 through mid 61. Apparently I need something like this for the volume required . There will be issues like the 54-01 will need a phono switch or possibly jumpered so it is always on. This will be a project that will take a couple of months. In the meantime the stereorama is going out in the garage. Got to have music while working on sound machines. Hydro

[William]

Hydro, was the fuse installed when the rebuild was done? Fuses are installed to protect the PT from frying. So, if the fuse did its job the PT should be ok, which is a good thing.

I had an issue with my Magnavox Berkshire a couple of years ago. I had returned from AZ and of course while gone the heat was turned down. The Berkshire is located in the family room in the basement and the basement takes forever to warm back up from having the heat turned down. I was working in the shop and decided to listen to the Berkshire, I turned it on, and instantly the fuse blew. So, my plans for the day changed and I pulled the guts out of the Berkshire. I went thru everything, found nothing wrong but the blown fuse, replaced the fuse, fired it back up and it instantly blew the fuse again. What the!! At that point I had no idea what was wrong. I reached out to a friend on the forum. I told him the story, and, he made a suggestion which is something I would never have thought about in a 1000 years. He said when vintage tube stuff is cold, and this was below normal temps because of having the heat turned down, it will draw more currant on start up. The original fuse was right at the line for currant draw. With it being cold in the basement it took more power to get the Berkshire going. He suggested that I install a larger fuse and then see what happens. I went up 1/2 amp in size, and, have not had any problem since. I do not know if this could be a possibility for your failure. I believe in your area you had cold, snow, and not normal weather lately? Your stereo is located in the garage, and not heated? This is my 2 cents for the problem you have. It might be a simple solution by just replacing the fuse. What ever it turns out to be, I wish you luck.

Bill

[electra225]

You can also measure resistance from B+ to chassis. Rectifier cathode to chassis. If it reads nearly infinite ohms, Something over a megohm or so, you don't have a short and can replace the fuse while monitoring current. If it has 500,000 ohms or lower, this indicates something in the B+ circuit may be drawing too much current, must be investigated and corrected before powering up again. I use big speakers on my bench for test. A clock radio should be able to power CG speakers without any problem. Maybe not very loud, nor sound very good, the clock radio should power the speakers no problem. The AMP 175 shouldn't have an issue with powering CG speakers.

[William]

Thanks, Greg. I forgot about mentioning doing some diagnostics before just replacing the fuse.

Bill

[Hydrolastic]

Hello Guys. I want to someday get to the point where I can get around a amplifier chassis or possibly align a preamp/tuner . But for the first couple of the consoles I had Sam at Sound audio repair install a fuse holder and isolate the chassis. Not sure exactly what it does because I see the the line is grounded along with the green ground lead?
It has been cold really cold for the PNW. Below freezing temps. Not complaining because I know the rest of the country gets it way worse than we do. Our problem is every year its the same thing. The stuff is just not designed to handle the cold. For instance last night in this house I woke up at 2:00 am to the sound of running water so I got up and with a flashlight and digging around in the Rhodi's I found a hose bib that had cracked and it was spraying water. Looking closer it was just a regular copper bib not rated for freezing temps. I looked at the other ones and they are the same. The ice has started to melt so it should not be a issue after today.
The garage was cold and I did have a heater going while working in there but it only helped a bit, prolly was in the 50's. So the tubes starting up from freezing temps is a definite possible cause of failure.

[Hydrolastic]

Hello, Forgot to post the photo of the inline fuse that sam installs. Hydro

[William]

Hydro! What size fuse was installed with the rebuild? Was it a slow blow? The formula for calculating amps is (watts divided by volts). Both numbers should be on the back of your stereo. For safety, you can take it back to Sam, or, this might be the perfect time for you to roll up your sleeves and dig in. If I can do it, so can you. And remember there is all of us to give you a helping hand. My guess, and I'm probably wrong because I usually am, the fuse blew because of the cold.

Bill

[electra225]

A Kill-A-Watt would make short work of troubleshooting. You could find exactly what current draw is so you will also know if you have the right size fuse. You could check it both cold and hot. Good luck.

[Motorola minion]

Fuse sizes of the fast variety, "AGC" are considered close enough if they are double the current of transformer primary. Unfortunately Zenith took this to an extreme to the tune of 4x primary current on most of their 59-65 offerings, resulting in transformer failures should there be a shorting filter cap, 5Y3 fail, etc.

In addition to a 3 amp "fast-blow" the AMP-175 in my 1ST208 is further buffered from high line voltage (122+) using two 2.7 ohm dropping resistors, CL-90 surge limiter (120 ohms cold) all in series. Its slow starts look awesome as the #47 dial lights come on slowly. I recommend this as I have 5+ years of no fuses blowing.

The Motorola amps use a 2 amp circuit breaker, slower than a fuse, resettable unlike an "MDL" rated slow-blow fuse.

For some reason, Magnavox and RCA did not use fuses or breakers to protect transformer primary windings, possibly relying upon the transformer to open its winding as a form of integral "protection".

.

[TC Chris]

Zenith's goal was probably to keep the house from burning down, not to protect the power xfrmr. Maybe Maggie figured that if you could afford their console, you probably had insurance anyway....

Chris Campbell

[electra225]

The deeper I dig into Magnavox, the more I see where they cut corners. A fuse is cheaper than a power transformer, even if you have to dig the chassis out to replace the fuse. I like the idea of using a resistor in line to cut voltage.