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Messages - psafloyd

#1
Guitar News / Re: Behringer releases SM57 clone
January 29, 2020, 11:41:28 AM
Tight with schematics, as they generally clone stuff these days.

I think the days of low quality Chinese knock off Behringer are long gone.

I know people with stuff they swear by in the studio and live, whereas I've only got a couple of their things and they work well. But as you say, the compromise to make a low price is in the materials.
#2
The Newcomer's Forum / Re: I want to ask a question
October 22, 2019, 03:43:11 PM
Isn't that a ProAmp badged as KMD? A little Essex-based company with (tenuous) links back to Selmer?
#3
The Newcomer's Forum / Re: Peavey Audition Plus
October 17, 2019, 03:24:56 PM
I see there are TDA2040s and TDA2050s freely available on ebay from China. They're cheap as chips, but I'm sure I read that they are often copies and not of great quality.

I have seen TI LM1875s on Mouser, so it would seem to make sense buying from there if I find the filter caps are not the cause. After all, cheap is not good if they blow easily or don't work full stop.

Quote from: Enzo on October 16, 2019, 10:44:21 PM
The Audition Plus is its own model.  You can get this or any other Peavey schematic from the factory:

customerservice@peavey.com

This amp, like many other small amps, uses a power amp IC to drive the speaker.  This  one is a TDA2040.  A TDA2050 would also work.  Those TDAs are no longer common, but an LM1875 should be a good substitute.

I point that out because it is almost certain your amplifier IC is bad.

One possibility to check first is a failed filter cap on one of the power supplies.  The two large-ish capacitors over near the fuse.  Any of them cracked free of the solder?
#4
The Newcomer's Forum / Re: Peavey Audition Plus
October 17, 2019, 03:00:27 PM
Sorry, I didn't see that on the small screen I was using.

Have now got it myself. And I commend Peavey's customer support to everyone. Not only were they very prompt (half an hour and I had the pdf), but extremely nice and polite.
#5
The Newcomer's Forum / Re: Peavey Audition Plus
October 17, 2019, 09:55:00 AM
Quote from: willpirkle on October 16, 2019, 03:49:24 PM
Agree with previous reply - if you are new to this, I'd definitely try to get the correct schematic as well. Peavey customer service (at least here in the states) is usually very generous with information and help. The last thing you want is to be second guessing the components, part numbers, etc...

Will do. I'll be back.

Many thanks.
#6
The Newcomer's Forum / Re: Peavey Audition Plus
October 17, 2019, 09:54:29 AM
Quote from: DrGonz78 on October 16, 2019, 03:43:19 PM
Look inside the amp chassis and confirm if there is a 2030 type opamp power IC. Not sure how closely related your amp is to the schematic posted but we'll find out as we go. Start by confirming the 2030 and then we're off to the races.

Thanks, I will be back soon, once I have the right schematic.

#7
The Newcomer's Forum / Re: Peavey Audition Plus
October 17, 2019, 09:53:47 AM
Thanks, Enzo. When I get inside, I will be checking the filter caps, having been through some of these tasks in the past.

And thanks for confirming the difference. I spent a good time yesterday scouring for any indication it was a different model and I didn't find any.

I'll get back to you in the near future. Not this weekend, alas, due to the wife's brother being over from Geneva.   
#8
The Newcomer's Forum / Peavey Audition Plus
October 16, 2019, 12:22:33 PM
The prelude
I have acquired one of these amps that has a particular problem. Having searched the site, I realise that others may have had a similar problem and I am hoping someone might recommend a sensible plan of attack.

The problem
The amp is in lovely nick, but on firing it up, there is a loud steady hum. This hum is not affected in any way by adjusting the volume or any of the controls, including the push button channel switch.

On reading previous posts, I checked if the speaker moved in one direction on start up and it does. So, I measured for DC at the speaker and this came out at 9.5V.

I haven't had it apart yet, as it only came in today, but am hoping for a plan of attack. But if there is DC at the speaker, this points to one of a number of potential causes, and I wondered if someone might suggest which to tackle?

I cannot find the Audition Plus anywhere as a schematic, so wonder if the difference was just branding. I have attached the Audition 20 schematic.

A whinge about the paucity of adult education

And if anyone is wondering why I haven't learned more since my first posts, I have been trying. I even tried to find a part time/evening course in electrical engineering or electronics and its a nightmare.

There are no electronics ones any more – I KNOW there used to be. As for the electrical engineering ones, they are either long vocational courses, or do little more than qualify the individual in PAT testing.

If anyone knows of any in the east London/south Essex areas, I'm all ears. Or a good correspondence course.

The thanks
Thanks in anticipation.     
#9
The Newcomer's Forum / Re: Carlsbro Hornet (1970s)
October 16, 2019, 11:37:28 AM
As I was coming on for the first time in a while, I thought I'd post an update.

To all those who offered assistance, many thanks. After changing all the electrolytic capacitors, the amp was working far, far better, with a more noticeable wobble in the tremelo effect.

It's still not perfect, but I had to put it aside when I moved my office and I plan to go back to it this winter to see if I ca improve it and put it into a basic cabinet.
#10
There are at least two editions of the 158 Rage. The later/latest one had a switch to switch between modern and vintage voicings. If your one has this and the schematic doesn't, it could be more than the switch got altered.
   

Quote from: substatica on June 14, 2019, 07:20:54 PM
Q: Next time it kills the sound, leave it running, ball up your fist, and whack the top of the amp.  Does the amp come back on, even for a moment?
A: No.

Q: Does the amp react to your whack in ANY way, like a noise?
A: No.

Q: When it dies, listen CLOSELY to the speaker, is there any background hum or hiss? 
A: Yes.

Q: Turn up the controls to hear that better potentially.   If there is any such background, to the volume and tone controls affect it at all?
A: Low hum, not affected by volume or tone, buzzes louder if I short the signal cable with my thumb.

Q: Get the schematic from customer service at Peavey, and then see if your power supplies are remaining up or if they are going out.
A: 120VA into the transformer, 25VA out  in the no-signal state.

Q: With it running and signal applied, poke each part on the board with a wooden chopstick or similar.
A: No effect.

I tested the diodes, they all read good except for the two 1N4003's by the power transistor, they short both ways -- maybe that's expected? It also seems if I leave it on in the no-signal state for 5 minutes or so the power cycle no longer fixes the issue, I'll have to wait and see if it works again after being off for a while. That brings me back to heat, but nothing on the board seems overly hot (hit it with infrared thermometer).

Also, still trying to determine if that's the correct schematic. It's a Peavy Rage 158 w/ Transtube, but the component markings aren't all matching up. The initial sold solder I fixed was on an R49 which I can't seem to locate.

The amp is the same as the one pictured on this thread,

https://www.diystompboxes.com/smfforum/index.php?topic=97068.0
#11
The Newcomer's Forum / Re: Carlsbro Hornet (1970s)
February 20, 2019, 01:09:49 AM
Quote from: phatt on February 19, 2019, 06:29:24 PM
Quote from: psafloyd on February 19, 2019, 08:55:57 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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#12
The Newcomer's Forum / Re: Carlsbro Hornet (1970s)
February 19, 2019, 08:57:09 AM
Quote from: galaxiex on February 18, 2019, 06:38:09 PM
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.

#13
The Newcomer's Forum / Re: Carlsbro Hornet (1970s)
February 19, 2019, 08:55:57 AM
Quote from: phatt on February 19, 2019, 02:37:49 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.
#14
The Newcomer's Forum / Re: Carlsbro Hornet (1970s)
February 19, 2019, 08:54:21 AM
Quote from: Enzo on February 18, 2019, 05:46:00 PM
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.
 
#15
The Newcomer's Forum / Carlsbro Hornet (1970s)
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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