Rare Ampeg Portaflex B-15-N Bass Amplifier - Major Repair [1/3]
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- Опубликовано: 12 сен 2024
- Oh dear god......
When I saw this I wasn't sure what to make of it. I was pretty sure that whatever happened it was not repaired to code and it was not going to look nice under the hood. Furthermore some 1970's air conditioner is missing a power cord.
This transformer is HORRIFIC!!!!!
The amp itself though is pretty cool, this particular one is a rare breed of B-15-N. You can tell from the 5U4 rectifier..
Opening the back cover we see the electrolytic quad cap that will need to be replaced followed by the removal of all of the tubes for testing. This is the LAST project to exclusively use the Century tube tester for testing as i transition in the Hickok 6000 this month.
Since my Hickock 6000 was not ready, I did go down to cornerstone and borrow theirs, also providing for some comedy relief. This was brought about by my inability to test the 6SL7 tubes on the century. and also because my Hickok is also ready.
After testing, the amp was simply to disgusting to work on so I had to stop and clean it, and vacuum it.... and re-clean it.... and then disassemble it. Hey, theres a treasure map inside under a layer of dirt!
This map tells us that the quad cap is actually wrong! the first of many wrong things in the amp. Jesus!!!! Look at the power cable, its not even soldered. Its tied in!
Theres also a soldered in fuse just hanging in-line, no rhyme or reason... no mount either, bet its high voltage that can short onto other connections.
Impressively, cathode bias is tied to the humdinger circuit.... cool!
This is the time to Deoxit everything.... I don't like this part, but it is necessary.....
The replacement monstrosity that was installed in the cabinet was drilled through. Whoever did this should find a new line of work. So i decided to remove EVERYTHING that didn't belong in the amp.
Starting with that nasty transformer.....
The schematic mentions a thermistor, which this device is missing. This is a curiosity but many of these actually did not come with them. It was not so important with tube rectifiers as it was with solid state. With new CAPS its even less important.
Due to mental health issues I decided to measure ESR for all of the coupling caps. But then common sense prevailed and I moved testing to the IT-11
Hey that 7.5k resistor is 1.5K.... Hmmm looks like components on the supply side were swapped to accommodate the Abrams tank that was powering this unit previously.
Im running out of tape.... time to flip this beta cartridge to side 2.
![Rare Ampeg Portaflex B-15-N Bass Amplifier - Major Repair [2/3]](http://i.ytimg.com/vi/9S7y_bG84Nk/mqdefault.jpg)
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EXCELLENT stuff here! I will get back to you with some questions as I am having almost THE SAME nightmare with the '63 B15N....
It was a customer AMP, long since returned.
18:38 - The components in those 'couplets' are shown in the tone circuits on the schematic.
Great video series. I didn't catch the assessment of the molded caps and if they passed the leakage testing. I guess they passed as they weren't replaced in part 3, but how did they actually do?
If I didnt post it, Im sure they passed, I would not have left them in if they were leaking.
Man that's really cool what does a service like that cost?
Extensive repairs and rebuild of a B-15-N?
@@retrotechandelectronics I have this exact question. I'm thinking you know a lot more about these than some local rando amp repair guy.
Hello! Cool video. I have one of these guys in the closet. Played it 20 years ago until the fuse repeatedly blew. Rather than damage it and not able to afford an extensive repair, I moved on to other amps. Now interested in repairing it. Know anyone who does work on these in the Miami area?
Sorry, I dont know anyone that far south.
Interesting vid ! As always it confirms that there are too many "repairmen" who know's it all...or do they really?;) Like "I can mod your amp" yeaah right...nice to see one that knows the shit!
All of the corrections here were done in accordance with the original schematic, if previous people followed that, it would not have ended up like this mess.
I've submitted "Deoxitadid" to Webster for inclusion in the next edition. We can only hope. :)
Last time I got too much crap for saying Deoxificatiated, so I shortened it....
I'm sorry I was so hasty in my submission. Deoxificatiated is WAY better. LOL
The act of implementing the process of Deoxificatiation.
Arnold Rimmer, removing all that grunge and debris might count as "Detox- ification"!