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Old 9th Nov 2019, 9:46 am   #1
Alan's MagicEye
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Default Homebuilt Copy of Ampeg B15 Bass Amplifier

After seeing the excellent post recently about the homebuilt Fender Combo on the forum, I thought that I should put a link here to my home brew Ampeg B15 bass amplifier and speaker which I made some time ago.

YouTube link here:

https://youtu.be/Elnz8E32EY0

I wanted to recreate as near as possible, the original B15 and put in the various options, for example, solid state or valve rectification, fixed or cathode bias etc. as the B15 was made with these different options over the life of its production.

After a bit of research I found some details on the net of a build which met my spec. on an Australian website (CtG electronics)

Link here:

http://ctgelectronics.weebly.com/cus...-fcbn-51b.html

I used this with some modifications to the biassing arrangement which I felt did not work correctly on the schematic provided by CtG. I also added a hum balance pot to the design.

The transformers were ordered, custom wound from Majestic Transformers in Poole, UK.

I managed to get a 15 inch driver from a Hammond PR40 tone cabinet which I understand was the same driver as fitted to the early B15's from eBay for 30 which I thought was a good outcome.

I'm very pleased with the result and have used the Ampeg at a small local gig which I do regularly. It sounds equally good with electric bass and double bass and I have had positive comments about the amp so I'm quite pleased that the gamble of making a homemade copy has paid off.
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Old 9th Nov 2019, 9:56 am   #2
GrimJosef
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Default Re: Homebuilt Copy of Ampeg B15 Bass Amplifier

Beautiful work !

The screen printing is a very nice touch. Did you find that it worked first time or that there was a bit of trial and error before it turned out so well ? I sometimes get Leak valve hi-fi amps in for repair and most of them were screen printed. This makes restoring the paintwork all but impossible without sacrificing the original labelling. It would be nice to know whether or not reproducing the screen work would be practical.

Cheers,

GJ
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Old 9th Nov 2019, 10:06 am   #3
Alan's MagicEye
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Default Re: Homebuilt Copy of Ampeg B15 Bass Amplifier

Thanks GJ

I had some trouble making the screen, the original screen which I purchased was pre-coated and was supposed to be suitable for exposure in sunlight but was a dismal failure. I then stripped the screen and brought a kit from Amazon

Link here: (Hope that this is okay with forum rules as it is hopefully relevant to your question)

https://www.amazon.co.uk/Speedball-D.../dp/B0007ZHGWI

I exposed the screen as per the instructions which came with the kit using a photo flood lamp with "pie tin" reflector. The result was very good.

As for the printing, I had several goes, but when the print was not good I simply wiped the paint off with a rag and had another go.

It would be a good thing to use on those old wonderful Leak amplifier chassis for restoration in my opinion.
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Old 9th Nov 2019, 10:07 am   #4
Diabolical Artificer
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Default Re: Homebuilt Copy of Ampeg B15 Bass Amplifier

Outstanding work and attention to detail.

Andy.
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Old 9th Nov 2019, 10:23 am   #5
Alan's MagicEye
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Default Re: Homebuilt Copy of Ampeg B15 Bass Amplifier

Thanks Andy

I'm glad that you liked it. It was quite a satisfying exercise, lots of different challenges to get the job done.....

Alan
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Old 9th Nov 2019, 10:36 am   #6
GrimJosef
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Default Re: Homebuilt Copy of Ampeg B15 Bass Amplifier

Quote:
Originally Posted by Alan's MagicEye View Post
... As for the printing, I had several goes, but when the print was not good I simply wiped the paint off with a rag and had another go ...
That's how I imagined it would be. Direct onto stainless I'm sure that works perfectly. I haven't checked the Leak paintwork closely, but I think it may be a three-layer process: base coat (bronze, or grey, or champagne) then screen print then (maybe) lacquer. I'm a bit concerned that wiping the screen print paint off the base coat without affecting the base coat at all could be tricky, especially if it has to be done several times. Doubtless it will depend on the finish on the base coat (gloss or matt) and how long it's been left to dry completely, maybe with a bake, before the screen printing is tried. Whether the screen paint (ink ?) is solvent-based or water-based might also matter.

Cheers,

GJ
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Old 9th Nov 2019, 10:58 am   #7
Alan's MagicEye
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Default Re: Homebuilt Copy of Ampeg B15 Bass Amplifier

Hello GJ

Yes, the consideration of the wiping is probably an important one.

Perhaps if the base coats on the chassis were in cellulose and you used something like "Humbrol" for the lettering, which I think can be wiped off with white spirit, then I think the base coat should not be affected?

I restored an old Lorry some time back and I used polyurethane paint on the majority of the vehicle but black cellulose paint on the petrol tank so that it would not be damaged by petrol spills. I would guess that Leak probably also used cellulose as the original paint?

You could do a simple test on a sample before deciding which combination would work I suppose....

Alan
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Old 9th Nov 2019, 11:35 am   #8
Craig Sawyers
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Default Re: Homebuilt Copy of Ampeg B15 Bass Amplifier

I had no idea that there were silk screen lettering kits - must find out more.

Craig

PS Stunning job on the Ampeg!
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Old 9th Nov 2019, 11:41 am   #9
GrimJosef
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Default Re: Homebuilt Copy of Ampeg B15 Bass Amplifier

Print-making is quite a popular craft hobby, it seems, and expert groups can sometimes be found. I did wonder if contacting my local group would be a quicker way to get up the learning curve. They are primarily creative artists whereas my problem is strictly technical. But they do seem pretty well equipped https://www.oxfordprintmakers.co.uk/equipment.html. I wouldn't be surprised to find they had a good deal of expertise too.

Cheers,

GJ
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Old 9th Nov 2019, 12:00 pm   #10
Alan's MagicEye
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Default Re: Homebuilt Copy of Ampeg B15 Bass Amplifier

Seems that GJ posted whilst I was typing my response, here it is anyway:

Hello Craig

Just to clarify in case you are unclear (apologies if you are clear ;-) the link to the silk screen kit in my earlier post is just for the photo emulsion and screen stripper for removing old emulsion.

The process is as follows:

Buy a screen which is suitable for the paint you wish to use, they come in different mesh sizes, from memory you need a smaller mesh for solvent paints than for the ink used for T shirts etc.

Obtain the emulsion kit and an emulsion applicator together with a squeegee (not sure if I spelt that correctly) which is a suitable size for the screen.

Mix and apply the emulsion to the screen in a low light environment using the applicator and allow to dry in the dark.

Make your artwork on a PC or Mac

Print (I use a laser printer) onto clear film, transparency media.

Lay the film on the screen and hold down with a sheet of clear glass and expose using a photo flood lamp, the instructions for this are in the emulsion kit.

Wash the screen to remove the unexposed areas where the artwork was and dry the screen.

Position on the job to be printed and squeegee the paint onto the surface of the job.


Hope this helps.....

Alan

Last edited by Alan's MagicEye; 9th Nov 2019 at 12:06 pm. Reason: Another post arrived whist I was typing
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