I have a Carlsbro Scorpion amp in a Hornet combo ( I swapped out as they seem to be exactly same amp unit..and I am using the 2 x 12 combo now with Hornet sounding nice). The problem I thought was just caps ..there are 2 big Erie blue ones 1000uF 63 v DC .. one looked 'blown' and I replaced with new of same value for both although other is still working ok. However .. the 'fix' only lasts for 30 seconds approx then original fault comes back which is no sound and when rotating VOL knob a loudish noise. If I turn off amp for about 10 minutes it works again initially for 30 seconds then ....as above....
If anyone knows what fault might be and guide me what else to replace be much appreciated... there are other smaller caps in circuit but all look visually good.
*note the Hornet amp I swapped out had 3 x 1000uf 63v caps instead of the 2 in this one... just sharing this incase it has bearing
I will try upload photos with this ... am new member here so be gentle with me
thanks
If anyone knows what fault might be and guide me what else to replace be much appreciated... there are other smaller caps in circuit but all look visually good.
*note the Hornet amp I swapped out had 3 x 1000uf 63v caps instead of the 2 in this one... just sharing this incase it has bearing
I will try upload photos with this ... am new member here so be gentle with me
thanks
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It helps a LOT to have some clue about the amp. There's many ways to skin a cap.
I have found a "Scorpion" with different knobs and maybe power but very similar parts. I've pasted the images and will attach.
I also find in my scrap-folder a "Carlsbro" transistor amp which is a later/bigger model, only the poweramp.
Differences noted:
Yours - Treb, Bass, Pres, TRsp, TRde, Vol --- 1000u 40V
His --- Gain, Treb, Mid, Bass, Revb, Vol --- 2200u 25V
Attachments
There does not appear to be a record of the schematics. The model described is not what it actually is.
Basic fault finding comes to mind here; Does DC appear on the speaker terminals? Does it get hot? Is the power supply to the 741s OK? Does any offset appear on the 741 chips, pin 6?
Could it be a Hornet 45?
Basic fault finding comes to mind here; Does DC appear on the speaker terminals? Does it get hot? Is the power supply to the 741s OK? Does any offset appear on the 741 chips, pin 6?
Could it be a Hornet 45?
Not sure why you left the old dead capacitor hanging in the air with *one* leg soldered ??????
Start with amp OFF, turn it ON with meter set to 200V scale, across speaker terminals ... do you measure any DC voltage there, specially after it starts humming?
Do this test before any other, we don´t want your speaker burst in flames while you measure something else.
*After* we are happy with this issue we proceed with the rest.
Start with amp OFF, turn it ON with meter set to 200V scale, across speaker terminals ... do you measure any DC voltage there, specially after it starts humming?
Do this test before any other, we don´t want your speaker burst in flames while you measure something else.
*After* we are happy with this issue we proceed with the rest.
Thanks for responses so far. I will just try to clarify. I am not expert only able to swap out components but I have a multimeter and will try do as you state. I am in rehearsals for a short tour at moment and time limited .
To answer JMFahey about leaving capacitor attached by one leg... because that cap is OK and is now fully attached again... to remove without cutting leg meant a hassle unsoldering the circuit board to get soldring iron to that leg.
I thought I had made it clear but will state again.. this amp circuit is the Carlsbro Scorpion ( it just happens to be in a Hornet box) but they are basically the same and these amps are the early ones from about 1974 ...not later ones... early ones have vintage looking grey check speaker cloth.
The amp doesnt hum.
It works for 30 seconds as normal... with guitar plugged in then quickly fades to nothing... see original post as to what I say.
I was just hoping someone here might have experience with this exact amp combo and know what old defunkt parts to replace from my description of the fault .....
If its too complicated for me as a layman I will have to send amp circuit to be fixed by a tech.. but before I did that and have to spend £XX per hour etc.... I thought I would ask here first incase its an easy fix and someone familiar with these Carlsbro ( because they sold a lot and lots still around) would say... " oh ..yes you need to replace all those caps or whatever and then id have fixed it... "
I appreciate so far all responses...
To answer JMFahey about leaving capacitor attached by one leg... because that cap is OK and is now fully attached again... to remove without cutting leg meant a hassle unsoldering the circuit board to get soldring iron to that leg.
I thought I had made it clear but will state again.. this amp circuit is the Carlsbro Scorpion ( it just happens to be in a Hornet box) but they are basically the same and these amps are the early ones from about 1974 ...not later ones... early ones have vintage looking grey check speaker cloth.
The amp doesnt hum.
It works for 30 seconds as normal... with guitar plugged in then quickly fades to nothing... see original post as to what I say.
I was just hoping someone here might have experience with this exact amp combo and know what old defunkt parts to replace from my description of the fault .....
If its too complicated for me as a layman I will have to send amp circuit to be fixed by a tech.. but before I did that and have to spend £XX per hour etc.... I thought I would ask here first incase its an easy fix and someone familiar with these Carlsbro ( because they sold a lot and lots still around) would say... " oh ..yes you need to replace all those caps or whatever and then id have fixed it... "
I appreciate so far all responses...
Sometimes bad / intermittent / loose fuse may cause electrical problems such as power loss. Not an expert myself but if you have a DMM and provide some voltages I'm sure lots of people here would help you to find the problem, as long as you know about the safety pattern while playing inside the amp.
to hex69 - its not power loss... read what i say. it works..... for 30 seconds , as normal...guitar plugged in ... normal... then it quickly fades to zero but the amp is still powered up.....so maybe its something like some other caps or ? that only works for 30 seconds then not..... BUT if i power amp down and wait say 10 minutes .... it will work again but only for 30 seconds...... so what could problem be? its not a fuse... no fuse is blowing
When you say 'the amp is still powered', what are you basing that on?
The LED (going off circuit attached earlier) is before the main power supply and so would still illuminate even if the rails dropped out. Fading out suggests some time constant at play such as a collapsing rail or a leaky cap affecting biasing.
First tests are ALWAYS to measure and confirm ALL the rails are correct under the fault condition.
The LED (going off circuit attached earlier) is before the main power supply and so would still illuminate even if the rails dropped out. Fading out suggests some time constant at play such as a collapsing rail or a leaky cap affecting biasing.
First tests are ALWAYS to measure and confirm ALL the rails are correct under the fault condition.
ok..i think i understand .... its still powered or appears to be because when i turn the volume pot at certain point on pot a loudish 'noise' is made thru speaker..... i have a gig in Paris ( as drummer) tomorrow so next week i will get my multimeter out and try and do the checks you guys have stated.... im learning.... and I thank you and everyone for your replies....
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