BassmanPaul

@Nibody I'm sorry for your medical woes. Having lived through two heart attacks, open heart surgery nd three strokes I feel for you. I hope that you re much improved as you read this missive.

So the amp is no longer a Fender Bassman! LOL I withdraw my comment.  

1 hour ago, ossyrocks said:

I know, you’ve said it before when I’ve talked about this amp. But, this is a ground up re-imagining of a Bassman, it’s shaking the house and staying clean up to around 5 on the volume at the moment. It might get louder, but I haven’t had the courage to try it yet.

Yes I have said it before and I'm not trying to rain on your parade. It's just that the huge disappointment I felt with that Blonde Blackface amp and matching twin twelve was so mind numbing that even today I get the shivers thinking about it.

For interest what was done to the amp??

I too was successful using a Bassman head into a slant front Marshall 4x12.  That said I still had to push the amp more that I liked.

Worst case stick a microphone in front of the cabinet.

I couldn't gig with a Bassman back in the Sixties so you'll need some support unless you just like fuzz bass.

More equipment has been permanently damaged by following advice such as this! Indiscriminate spraying of contact cleaners inside a piece of equipment by someone who has no idea what that person is doing can cause more harm than good.

Following agedhorse's sound advice given on February 24 is the only sensible/safe route to follow..

Take single triode section from a 12AX7, cathode is grounded, grid to ground via a very high value resistor. Signal connects through an isolating capacitor. This is a positive bias stage. Looking through schematics you can see this used time and time again.

Back in the day tube tape recorders used the scheme to match the high impedance of Chrystal  microphones

Keep us informed about developments and good luck.

Doesn't confuse me one bit!   Even though it can be variable to ensure correct bias level at set up, once set it doesn't vary so is fixed. Virtually everyone in the amplifier field refers to the arrangement as Fixed Bias. 

Just noticed you're from Swindon. My Dad's family hailed from Swindon.

On 06/02/2024 at 06:53, joel406 said:

Hartke has never impressed me. The new stuff is the worst they have ever made. No power, no body and worst tone in the business. 

Come on Joel tell us what you really think!! LOL

For some reason I have yet to measure the output capabilities of my B15 unit. From the diagram and voltages present it should give at least 45 odd Watts. 

BTW @JapanAxe the correct term is Fixed Bias and not grid bias. 

White noise is a product of all active electronics. Some folk are more sensitive to it than others. Same goes for fan noise. In reality, on stage, neither would be audible. 

I have built hundreds of amps over the last sixty years.  The Ampeg B15 is a very simple build. You should stick to the circuit exactly and use the 6SL7 octal preamp tubes. They have a certain 'something' that adds to the B15 mystic.  I have every thing I need including chassis to build six more amps. As winter progresses I'll make a start on the first.

I'm thinking of a B15 clone using a pair of KT66s that I've had in my tube stores for years. Time to put them to good use.

I already own a B15NF and whilst reconditioning it I ran into Two problems. After installing new caps I experience flash over in the GZ34/5AR4 rectifier. the cure was to add a fast recovery silicon diode in series with each plate/anode of the GZ34. The second was the 6L6GCs red plating in spite of the negative bias being correct. Cure was replacing the 270KΩ grid bias resistors with 100KΩ as per the RCA tube manual. I feel that the amp is sensitive to the 'new' tubes being produced today. 

Good luck with the build. It's very rewarding when you step out on stage using equipment that you put together with your own hand!!

Unfortunately it's not as simple as that and you might just make things worse. When disaster strikes if the item is of good quality it's worth putting money into it to promote reliability. 

Remember that flood water also contains sewage. Yuck!!

For some reason I got it into my head the Positive Grid were based in the UK.  on checking they seem to be in Las Vegas! LOL

I have never even seen one of Alex's Barefaced cabinets so I cannot comment on that score.

I use the Acme Sound B2 three way cabinet. I'm certain that one would cover most gigs but I am conservative with my gear. I stack them on their ends so the divers are vertically aligned. They work better that way all around. Two stacked atop each other of a vertical 4x10 is my go to amplifier system. I always use the pair whenever I gig.

Newer drivers are more capable so I bow to BFM's wiser knowledge base. That said I can't imagine being able to successfully play a gig with just one ten.

19 hours ago, Merton said:

(For clarity, I made the drummer physically sick at last week’s rehearsal co if the high SPL … just for fun, y’know 😬)

I fear for your ears. It's no fun being deaf and hearing aids are expensive. My current pair cost six grand!! 

I'm sorry for your troubles I really am. I would consider sending it in to the manufacturer for their opinion. Water, especially filthy flood water, is not a healthy thing for any amp class D or no. Water would likely have gotten into the pots and switches. I don't think any manufacturer would gouge you with excessive fees for such an event.

Two cabinets always sound better, fuller than just one.

@sandy_r Thank you for taking the time to help out.

Thank you for the kind words.

On April 04 1981 Lionheart played a formal at Toronto's Ontario place. WOW!!! That's 42 years ago! It only seems like yesterday. On an impulse we dangled a microphone over our light trees on each side of the stage. Connected to a cassette recorder we let it run. What came from it was surprisingly good and pretty well balanced. This recording I  copied onto my computer and then burned to CD. I got them out and listened to the entire night. LOL  It showed just how good John's playing was. His vocals are amazing. He was trained a St Micheal's Choir School here in Toronto. 

I wish I could post a bit but the files are all too large. 

Today I am deeply saddened to hear that the Keyboard player from the best band I ever played with has passed away at the age of 71.  We lost our Drummer Dennis to cancer and now John has gone.

As a band we shared such adventures going to gig after gig here in the Toronto GTA and across Southern Ontario.  The music wa played was wonderful. Our Beatle medley was such fun. Forty five minutes of non stop Beatle music.

Rest in peace John. 

Edit: I know this is the wrong place for this but if anyone could understand how I feel it would be other musicians.

For anyone who plans on working on an amplifier it behooves them to at least learn the basics of electronics. Would you work on a car's engine without learning a bit about it before you start?

8 hours ago, Beedster said:

 

Many thanks @agedhorse, is this the sort of thing that if I get wrong I've wasted some cash, or if I get wrong I've damaged the amplifier?

With the greatest of respect @Beedster that schematic  is about as simple as one could be.  I could almost build that blindfolded!!

I broke a sweat just looking at that rack!!