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Messages - psafloyd

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1
The Newcomer's Forum / Re: Carlsbro Hornet (1970s)
« on: February 20, 2019, 01:09:49 AM »


What an eejit. It so clearly has.

Just goes to show I need those readers or a magnifying glass. Age has not only caught up but overtaken me this last year... 

Thanks, again, Phil.

Yep I know the feeling, my eyes also struggle to see fine detail. :'(
I don't even bother to try and fix anything that uses SMD's.  xP
I agree with *galaxiex* about replacing Electro's in old gear but I would add this;
Only replace the obvious first and get the amp working,,, then go back and replace the others.
If you shotgun the whole lot and it still does not work then you have no idea if you added yet another mistake. :-X
Phil.

Will do, Phil. Simple process of elimination far more sensible than having to pick the bones out of wholesale change. Thanks again.


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2
The Newcomer's Forum / Re: Carlsbro Hornet (1970s)
« on: February 19, 2019, 08:57:09 AM »
I have worked on quite a few SS amps from the 60's and 70's.

I've found in all cases those amps benefit from replacing ALL of the electrolytic caps.

I used to test them (caps) and leave them if they "seemed good" but the amp(s) would still have problems.

If that amp were mine I'd start by replacing ALL of those blue tubular electro caps.

Just my $0.02

Makes perfect sense. Nothing lasts for ever, after all.

Thanks for your tuppence worth.


3
The Newcomer's Forum / Re: Carlsbro Hornet (1970s)
« on: February 19, 2019, 08:55:57 AM »
C16 has popped,,so replace for sure.
What's the bet that is part of the trem circuit. ;)
Phil.

What an eejit. It so clearly has.

Just goes to show I need those readers or a magnifying glass. Age has not only caught up but overtaken me this last year... 

Thanks, again, Phil.

4
The Newcomer's Forum / Re: Carlsbro Hornet (1970s)
« on: February 19, 2019, 08:54:21 AM »
So you don't have this schematic, but if you can find other Carlsbro amps of the era, chances are the trem circuit is similar if not the same.

Thank you, Enzo. Struggling to find the same era.There seem to be plenty of the earlier and later valve amps or the later SS ones. But I'll take a look for the later ones and make a comparison.
 

5
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.

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6
The Newcomer's Forum / Re: Update on Londoner L100A amp
« on: January 09, 2019, 06:13:38 PM »
You don't need a 6A switch, you need a switch rated 6A or more.
If the 15A will fit, use it.
If not, post some pics and measurements (bushing diameter), I'm sure there are switches available that will work.

Thanks for the advice.


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7
The Newcomer's Forum / Re: Update on Londoner L100A amp
« on: January 07, 2019, 05:00:37 PM »
If the original switch can't be found you may need to look at mounting a different type of switch.
I assume the original is a round hole mount with metal toggle.
There are plenty of 10Amp plastic package rocker switches around now but they are mostly square cutout type.


Re the speaker socket.
Who knows why,, without seeing the unit I have no idea but a lot of amps do have a switching setup so that when the external speaker jack is used it turns off the internal speakers.
This avoids the low ohms issue that can often burn out the power amp.
If the parametric EQ pot is stuffed that will cause wacky sounds, the amp may even oscillate and squeal like a pig. :o
In my experience, the can of cleaner will only be a temporary fix and likely cost more than a new pot. 8|
Phil.

Yes, round hole metal toggle. Seen on/off/on ones, but most on/on are 15A. But most switches are the plastic rocker style as you said. Would mean cutting a larger hole in the panel.

The EQ pot works, but the depth pot next to it makes awful noises when moved.

Thanks again.


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8
The Newcomer's Forum / Re: Update on Londoner L100A amp
« on: January 07, 2019, 09:45:13 AM »
Yes 50k pot is the same thing.
i.e. when a schematic calls a resistor 5k you use a 4k7 resistor.
Except for maybe the bias it's rare in these circuits to need exact values.

To find out if the pots are linear or log just use your meter to measure end to end,, jot that down ,, now turn the knob to halfway and measure from wiper tab (Centre) to one end then the other.
If it's a linear pot it should read close to half the total value from both ends.
If Log,, it will read about 10~20% from bottom to centre and 80~90% from centre to top tab.

The burn marks are a common result as they are power resistors and do get very hot. Would be better to mount them on insulated stand offs but amps are made to a cost. If the heat is extreme the board can burn up and it can de laminate the copper tracks underneath but yours looks ok.

So Q?
Is the amp working?
if so don't replace parts willy nilly as you may cause a new problem.
Fix the pots first then see how it sounds.
Phil

Yes, the amp is working, or was. I am only going to change the pots and put on a new power switch which has failed – if I can find one at 6A 125V as all these seem to be mini DPDTs. Any ideas gratefully received.

When I last looked at the amp, it was powering on but making no sound. So I switched the jumper lead run from the speakers to the external speaker out on the back (in previous post).

I hadn't worked out why this had been jerryrigged before as it was sticking into the slave socket when I got the amp. Then it worked and pretty well, but I assumed the reason for it being done like this might be something to do with a problem elsewhere which this might bypass. That doesn't really make sense to me, as it seems to just loop the signal from the speakers back into the amp (and no doubt an external one). But if it works, why would that be bypassed? Anyway... 

There is some horrible sound when turning the depth pot on the double potted parametric EQ (which changes in tone with the EQ setting), though this may have improved with a thorough cleaning of the pots.

I can't test the reverb as the controls are broken off, but the tank looks in very good shape.

9
The Newcomer's Forum / Re: Update on Londoner L100A amp
« on: January 07, 2019, 05:39:56 AM »
Those are power resistors (1ohm, 5watt).  They are shown at the emitters of the power transistors in the 100S schematic.
If they measure 1 ohm or less with your meter, they are probably fine.
The pot looks like it says 'lin' on it, which would be linear.


OK, so if they register <1ohm, they should be OK. Can I measure them in situ, or do I need to detach one of the legs? (Sorry for the noob questions.)

The other components look OK, ie not obviously melted or charred, so perhaps it is historical or it just overheated some time.

I imagine I should probably check the big blue capacitors while I am in there , though I don't see any bulging, etc.

Thanks also for your eyesight. My near sight has become very middle aged over the past year and I missed that when I could normally read 7pt text in the dark!

But I haven't found any 47k pots and wondered if that means they are not readily available. Of course, it could be my eyes can't register the decimal as I know 4.7k are easily had, however, if 47k, am I right to think I cold replace those with a similar 50k pot. After all, that is within 10% of the tolerance set for many components?

Thanks again.   

   

10
The Newcomer's Forum / Re: Update on Londoner L100A amp
« on: January 06, 2019, 12:15:41 PM »
Need more info,,
Is it a resistor?  a Capacitor? what does it look like?
Try and take a pic of the part.
Phil.

Have managed to attach the pics this time.


11
The Newcomer's Forum / Re: Update on Londoner L100A amp
« on: January 05, 2019, 05:04:55 PM »
Need more info,,
Is it a resistor?  a Capacitor? what does it look like?
Try and take a pic of the part.
Phil.

I did upload some pics as well, but it would appear that didn't work. Will do it again.


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12
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.

         

13
The Newcomer's Forum / Re: Carlsbro GLX100 footswitch query
« on: January 04, 2019, 12:45:55 PM »
Thanks for that. I worked out the functions.


14
The Newcomer's Forum / Re: Carlsbro GLX100 footswitch query
« on: December 30, 2018, 01:17:19 AM »
Pull any function pin to ground & it will 'operate'.

Thanks for the advice.


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15
The Newcomer's Forum / Re: Carlsbro GLX100 footswitch query
« on: December 30, 2018, 01:16:14 AM »
Here is what I have for schematics. Not sure this is the amp that you have but it is something related at least.

Thanks for that, much appreciated.


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