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Topics - psafloyd

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The Newcomer's Forum / Carlsbro Hornet (1970s)
« on: February 18, 2019, 03:18:18 PM »
I have acquired an amp chassis (it was cheap as chips) to fiddle with.

Apart from Carlsbro, there were no other identifying marks, but I have now determined it to be a Carlsbro Hornet from the late 70s.

I have seen it described as both 30W and 35W but cannot find a schematic.

The amp seems to work well (a bit slow and fizzy powering down) but is surprisingly loud and will make a good pedal platform.

After checking for any loose or dried/charred components, I cleaned all the pots and they work well.

However, the tremelo is slightly off. I was warned something was amiss, but it only has one usable sound with the depth control set at about 0.5. This provides a little shimmer. Above that, it gets a bit odd very quickly. It quickly seems to lose a part of the swell giving it a touch of the Norman Colliers.

As I cannot find a schematic, can anyone suggest possible areas to check? I assume it is the circuit with the tremelo components, but am at a loss to identify them.

Also, I have only seen it as a vertical 2 x 10 configuration (pic attached) combo. I used a 1 x 12 to take the load at low volumes and assume the originals would have been 20W rated or similar.

Is there a way to determine the right size speakers with so little information?

And how does the speakers' impedence affect that calculation?

Any help gratefully received.

The help I have received so far (and gleaned) has allowed me to sell on a load of old kit I had accumulated with guitar purchases.

I sold the Gorilla for twice what it cost me. Another I got for a fiver went for just under £100, with a similar amount going to charity from those items alone.

Most of this was simple cleaning, reattaching and a little soldering, but it was the strategy that helped.

So far, the amount to charity is nearer to £250, so thanks to all who help. Just wanted to let you know others benefit from your assistance.

Sent from my SM-G960F using Tapatalk


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The Newcomer's Forum / Update on Londoner L100A amp
« on: January 04, 2019, 12:56:51 PM »
I posted on this amp last year but for a number of reasons, it got shelved.

I have launched a new topic as it is so Ling since I posted I feared people might not see it.

Anyway, had it apart today and think I understand why the speakers were being bypassed via the speaker out.

There is a second board behind the back panel with a large burn mark under one of these components marked 155-318.

Can you advise what these are? I'm struggling to identify them on the schematic (attached).

I am also struggling to find an on/on latching DPDT toggle that is rated at 6A 125V. I can get one, but seemingly only from China, so that can't be right. Can you recommend a trusted supplier you use for components that might carry these? The ones I have used for guitars and effects pedals don't seem to carry them.   

There are a number of potentiometers with broken shafts I was looking to replace. They are 47K board mounted pots with three pins but I can't work out – and I've been looking for an answer – whether these should be log or linear pots.

Any advice on these greatly appreciated as ever.

Many thanks.

         

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The Newcomer's Forum / Carlsbro GLX100 footswitch query
« on: December 29, 2018, 03:35:46 AM »
I picked up a well loved Carlsbro GLX100 that needed a bit of TLC – replacing both inputs and a lot of switch cleaner – but which otherwise works well.

It came with an aftermarket footswitch for the and I believe the second channel, but not the other (optional) one. This is wired via a 4 pin DIN plug and covers crunch and reverb (see image below).
 
I'm happy to try wiring a replacement with some CAT5 cable, but I've had no luck in finding a schematic. Even if I work out how to wire such a footswitch (I can crib another, I'm sure), I'm not sure how to go about determining what each pin does.

I am sure they must be as listed on the pic of the back of the amp below, but in addition to reverb and channel switch, could the others be power for LEDs and possibly a ground?

The other pic shows a footswitch from the same range which has a mix switch (like my Sessionette 75s), but I don't know how to work out what pin does what.

Any assistance gratefully accepted as ever.

     

4
Preamps and Effects / Seized pots on a Marshall Guvnor Mk 1
« on: August 06, 2018, 09:43:46 AM »
This isn't such a noob query as it may appear on first viewing. In 30 years of playing guitar, I have never come across this particular circumstance. 

I have picked up my Guvnor which I haven't used for several years, but which is stored on a shelf in a bedroom, so no excessive moisture.

When I plugged it in, all the pots were seized. All of them. I have tried using some cleaner to free them off, but I am stumped as to why five pots should all fail at the same time and in the same way.

There is no apparent damage to the unit and it all looks otherwise good inside – no dirt or corrosion. The pots are not over tightened on the chassis, nor are they misaligned in some way that would prevent them from turning.

I was thinking perhaps the excessive temperature we have had this summer may have caused them to dry out and lock up, but all five pots at once seems rather a coincidence. 
 

5
I picked up this amp for not very much as it wasn't working properly. From the description, it sounded like dirty pots so I took the plunge and bought it.

After giving it a thorough clean, the amp turns out to be not a bad amp – the 12" speaker undoubtedly helps – and all the issues were resolved. Except one.

When you turn up the reverb knob from off, a hum is gradually introduced. It becomes very loud at maximum, though I would never use reverb at that level.

The chances are I would never use the on board reverb, either, instead use EH Holy Grail Plus. However, I'm not planning on keeping this amp and would like it working fully to maximise the return as I sell these kinds of items to raise money for charity.

I cannot find a schematic – and I have looked – but I have attached some pics of the chassis and amp and here is a link to a piece of video demonstrating the problem.

https://youtu.be/kYj17XQkhdI

One thing I can tell you is the cable on the reverb is securely plugged into the tank and also the PCB. Whether they're the right terminals, I can't tell you.

Though I have done a lot of reading and YouTube viewing since my last post, I am an electronics novice and haven't a clue, so any tips gratefully received.

6
The Newcomer's Forum / Londoner L100A
« on: November 05, 2017, 08:10:07 AM »
I picked one of these up recently, mainly for an Eminence speaker that had been fitted bit if operable after a few fixes, I could pass it on.

I'm no electrical expert, but I had a look inside and apart from the easy replacement of pots that have had shafts snapped off, it all looked pretty clean.

However, there are two things I am a bit stumped on. Firstly, someone has wired one of the speakers from the slave socket and I can't think why.

The other thing is that each of the pots has had a continous piece of copper strand soldered across all the pots. Is this a backup groubd because you coukdnt trust the FDR electrics or possibly to resolve a grounding issue?

Any help gratefully accepted.

The model is identical to a Sound City RC100 and a Vermona Regent (the model the others sprang from and were renamed for export).

Sent from my SM-G925F using Tapatalk


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