Rare Ampeg Portaflex B-15-N Bass Amplifier - Major Repair [2/3]
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- Опубликовано: 12 сен 2024
- Work continues now that the parts have arrived to include the new power transformer and capacitors!!!!!! Apparently the transformer does not come with any SAE mounting hardware so its off to a trip to ACE.
This begins the mounting process for the transformer, having pulled all of the wires through. Finally I get to see what it looks like when it doesn't look hideous. Now the work begins; since I didn't swap an old one out ill have to take extra time to ensure which wire does where, and then match that up to the schematic. Having accomplished this I start making my connections. The ones I'm not 100% on yet i'm, leaving extra service loop in. Also the remnants of the old connections were removed and cleaned up.
The next job is the replacement of the quad electrolytic cap, which will have to be replaced and also inspected to ensure that the wiring is correct. The old mount is carefully removed and reused.
Also, that 1.5K has to go....... so Im putting in the 7.5K resistor as specified, along with the two remaining electrolytic caps. Also, finally installing the missing 20uf in the finals of the 6L6.
Finally the new power cord goes in to include a chassis ground off of the transformer bolt. Shorting tests are then done to ground and then through the power switch on the plug.
Ive decided at this point that AC would be measured from the tube sockets at a fraction of the voltage (40vac) using a Variac to ensure everything was wired correctly. This confirmed the wiring to be good.
The next test introduces the rectifier. But it did not produce a voltage. I was able to find that their is a missing section that forces the amp to standby when the speaker is missing. I had to make a jumper for testing.
With that, all tubes in, B+ is looking good.....
Out of tape again...... Flip to side C
Line hot from the wall should go the the fuseholder tip -- not sleeve -- to reduce shock hazard ... peace
great video! Do you recall where you sourced the PT. I need a 240v version for a customer's B15. Mojotone have a US version only. Many thanks.
Mr. Rubin do you know how to stop the speaker cabinet rattle in this very amp ? I have the identical model portaflex and it works great. I even had it up to Long Island to have Ollie give it an electronic tune-up.
But of course taking the train I could not bring the cabinet. The rattling is extremely annoying. Thanks
You could get the cabinet on the LIRR.... Unless you are going to Northport....then the transfer would not be fun. If I were looking for rattle in a cabinet I would not use an amp but a function generator, fund the rattle frequency, then determine if its a speaker or the cabinet, and where, adjust accordingly.
3:30 - Yellow - 5V rectifier filament
Red - 375V Secondary!
So you are commenting because I wrote rectifier heater and you responded with rectifier filament? and then commented on reds annotation being the AC input to the rectifier on paper for cable sorting, this one getting an apostrophe!!!!? Are you somehow insinuating that cables were crossed or backwards!!
No, they were connected correctly. you only misnamed them here. :)
What was the amplifier current draw?
the Specifications are coming out in the final video when fully populated and biased
I prefer to use nuts that have a star washer built into them so that you don't have to use a separate lock washers when installing and bolting down the Transformer. I'm surprised you don't have a coffee can full of used nuts and bolts and various related hardware from gutting and stripping down other pieces of electronic junk!
I do. But not SAE
Retro Tech & Electronics , I was able to buy boxes of SAE hex nuts (4-40, 6-32, and 8-32, although they didn't stock 2 - 56) with the built-in star washers at a chain hardware store, although it might not be something you would find at Home Dumpo. Finding metric versions of these nuts with the built-in star washers, however, can be very difficult, unless you buy them online, which quite frankly I hate to do.. Years ago we had a dedicated, local, single owner Fastener company that stocked virtually anything and everything you could think of, and they would order it for you if it wasn't in stock. They are long gone now of course, as is Sears Hardware which had a far better selection of metric and other oddball bolts and nuts and fasteners than any other big-box hardware store or home improvement store. of course, Sears Hardware is also gone now.
Why do you call it a death cap?
Before better safety standards or X2 rated caps, any old cap was used from main to chassis. If it failed as a short, well....... not so good.
@@retrotechandelectronics Got it. Do you recommend adding a chassis ground to an amp like this?
CJVideoProductions depends. Some amps are kept original so I use higher rated components but no ground. Others by request I modify and ground the chassis