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High power combos that go intermittant

High power combos that go intermittant after a period of use.

If they use an elbow jack on the amp to speaker link , replace with conventional, if poor manufacture. Check the internal construction and if poor mechanical connection at the elbow means the shaft can turn , with pliers , when cold, so a resistance and voltage drop, heating the plastic disc that is all that forces a mechanical connection. So progressively worsens, so when heated by the current, in use, the shaft will turn with finger pressure only rather than requiring pliers.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N Cook
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You must be talking about the really cheap ones. I usually do a little extra soldering on the ones I've used so it's not just a mechanical connection anymore.

Not if you do it right.

Also, If you put a straight jack on say, an old Fender combo, you better unplug it before you lay it on its back in the mini-van...

PS: It's called a right-angle jack. And if you're running enough current through it to heat it up, you might want to consider Speak-ons anyway.

-Dave

Reply to
Dave Curtis

Dave, I think he's talking about the right angle plug #228 Switchcraft or the even worse #220 which do really suck and can be easily damaged and become loose enough to be intermittent. The Switchcraft #226 is much more superior in design and reliability.

Reply to
Elvis Kabong

I thought he was talking even cheaper (RS/china), which is why I mentioned soldering the compression connection. I've done that to fix a spinning tip connection. You need a hot iron and do it quick.

Yes, we both meant 'plug'.

BTW, I seen (real) cheap straight jacks where the tip or sleeve would spin...

How's Amps, Ed?

I've got an intermittent Randall with a(nother) glued-on back, a

2X50watt Marshall to bias, and a sick MusicMan... CYA!

I need more benches! (actually, I just need to clean a few more off ;o)

-Dave

Reply to
Dave Curtis

Sheeks Dave, you *would* have to ask. Here's the rundown:

Just finished doing all I can do with a Marshall Model 2000 250watt lead head that I think the owner stressed the OT years ago by sticking 20amp automotive fuses for the external fuse holders even though there is at least an internal fuse to blow in case of that idiocy. Not only that and even though EL34s can handle the B+ the customer doesn't want to pay to have 6550s in it. But what happens every now and then, the protection diodes short and blows the mains fuse. I keep telling him this is going to happen when he cranks it since the OT seems out of whack. On the primary, I'm getting 57mH on one side and 68mH on the other. The output signal looks wacky too. What a shame. The amp is rare and the owner went and abused it. Can you imagine how much Mercury Magnetics would charge to rebuild the OT?

Also restoring a BF Twin Reverb head that was under water during Katrina. The fiberboard was like a roller coaster so I'm having to replace it with a Mojo one. Reinstalling all of the blue Moldeds and any resistors not out of tolerance and any pots that still turn. Took the PT apart to let it dry out and found that it had some sort of tar substance in it which means to me it must be waterproof, so I'm assuming all of the transformers are ok, that is until I fire it up once finished reassembling.

Just finished the HOSE amp version 1 (High Output Single Ended). High B+, switchable to 5AR4 or 5U4, one 6550 and two paralleled

12AX7s with gain, master and treb, mid, bass controls. Got it up to 17 watts even though the OT specifies 15 watts.

Just starting HOSE version 2: low output SE amp into an interstage transformer to a pair of EL34s. Hope I can get that wonderful tone of an SE amp preserved and amplified into a push-pull output to be loud enough for bigger gigs and not having to mic for a gig. Might turn out to be the best of both worlds - that sweet SE tone, yet loud enough to gig with and with more than just having a single tone pot. Considering installing a low output OT to also a low watt speaker for the practice amp/studio volume of a just a SE amp and making it switchable to either that or to the interstage transformer.

Soon there will be pics on Dave Moore's website. That's still in process.

Have fun,

Ed

Reply to
Elvis Kabong

Not actually required as a mechanical problems on a Marshall "Valvestate" VS65R. But I cannot find any details on the main components , ready for next time, or for anyone else coming across them , any pointers ?

Marshall T65 and its compliment T64A (curiously one suffixed A only), TOP66 package Motorola MJF 22 , also marked R91, TO220 package, not found on Motorola site

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N Cook

TOP66 ? Do you mean TO-220 ?

Resistors in TO-220 packages are not unknown. Possibly low inductance low ohms type. What's the function - and marking ?

Graham

Reply to
Eeyore

"Valvestate"

next

TOP66

ohms

The package that plastic 2N3055 come in like TIP3055, probably something like Marshall badged TIP3055/TIP2955 output pair

Reply to
N Cook

Oddball devices.

My big Motorola Power Devices manual lists nothing like it ! The MJFs have fully isolated packages btw. Is that the case here ?

Graham

Reply to
Eeyore

components ,

only),

found

low

fully

It was actually MJF122, the centre spine of the retaining clip had messed up the surface of the package and obscured the 1 , so plenty of info on that one

Reply to
N Cook

Complement is MJF127.

That's a fully isolated TO-220 package though ! Quite different to TIP3055.

Graham

Reply to
Eeyore

messed

that

TIP3055.

That was the small Motorola one, that I misread

The Marshall badged ones are probably like these 2, original specs, for the archives, both are the right TIP35/TIP3055 type packages

T64 = BDV64C T65 = BDV65C eg Part Number = BDV65C Manufacturer Name = Various Description = Darlington, PowerDarlington, Power BDV65C Si npn

125W 140V 120V 5V 12A 150>C - - 2000T PHI TO218-2

OR

T65 NPN silicon darlington power transistor. Complementary epitaxial base transistors in monolithic darlington circuit for audio output stages and general amplifier and switching applications. Magnatec Inc

ABSOLUTE MAXIMUM RATINGS (T = 25°C unless otherwise stated) case T64 T65

-120V 120V V Collector - Base Voltage (Open Emitter) CBO

-120V 120V Collector - Emitter Voltage (Open Base) V CEO

-5V 5V Emitter - Base Voltage (Open Collector) V EBO

12A Collector Current (d.c) I C 20A Peak Collector Current I CM 0.5A Base Current (d.c) I B 125W Total Power Dissipation up to T = 25°C P tot mb

-65 to 150°C Storage Temperature Range T stg

150°C Maximum Junction Temperature

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N Cook

Marshall are quite happy to supply semiconductor spares and have a very helpful service dept - once you get through to them!

Ron(UK)

--
Lune Valley Audio
Public Address Systems
Hire Sales Maintenance
www.lunevalleyaudio.com
Reply to
Ron(UK)

fully

el t65 y el 64 son darlington. buscalos como bdv65 y bdv64 reemplazo tip142 tip147. para el mjf122 el tip120 o 122

alexis cid de chile

Reply to
el pule

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