Hi Folks
...in my solitude here in the UK, I'm trying to fix a Crimson CPR2 Pre-amp that has 'lost' it's L.H. Channel.
Have removed/tested/found good all transistors in Line Stage.
Occurs to me that if the problem resides in the Disc stage, would this in turn prevent the Line Stage from properly functioning 'downstream'??😕
I've attached a pdf with pages showing both stages...
Scratching my head at the moment, which isn't a good idea from a hair retention perspective...😱
Any thoughts out there please??🙂
...in my solitude here in the UK, I'm trying to fix a Crimson CPR2 Pre-amp that has 'lost' it's L.H. Channel.
Have removed/tested/found good all transistors in Line Stage.
Occurs to me that if the problem resides in the Disc stage, would this in turn prevent the Line Stage from properly functioning 'downstream'??😕
I've attached a pdf with pages showing both stages...
Scratching my head at the moment, which isn't a good idea from a hair retention perspective...😱
Any thoughts out there please??🙂
Transistors rarely fail in preamps.
Most likely you have a bad solder joint or a bad punch block connection if you have such things. Also possible the volume pot or source selector switch is bad.Rarely a resistor or capacitor will lose connection with one end due to a bad weld. About the same incidence as transistors losing a connection.
Best thing to do is trace the signal through the unit to see where the sound stops. You can use a scope, I use a 2.5 VAC scale of an analog VOM. I put a .047 uf capacitor in series with the probe to analog ground to prevent response on DC sources. Analog VOM have no electrolytic caps to require replacement in 20 years. My Simpson 266XLPM meter was bought in 1987.
I use a cheap FM radio for a signal source, out the earphone jack. Turn down to 1/3 or less, earphones can go to 7 vac which is too much signal. If tuned to a rock station you can see the beats of the music on the meter probe. which looks nothing like ultrasonic oscillation, high & steady.
If you find a point that when you touch it it makes the sound flow, you've likely found the bad joint. So put the output to a amp+speaker while you probe.
When working a unit with the power on, wear no jewelry on hands or neck, 1 v at 50 amps can burn your flesh to charcoal. Use only one hand at a time, 25 v across your heart can stop it. Use an alligator clip lead for the ground probe. Wear safety glasses especially desoldering.
You poor Europeans and your hair. My native Am hair is permanent on my head, and not on my face or chest.
Most likely you have a bad solder joint or a bad punch block connection if you have such things. Also possible the volume pot or source selector switch is bad.Rarely a resistor or capacitor will lose connection with one end due to a bad weld. About the same incidence as transistors losing a connection.
Best thing to do is trace the signal through the unit to see where the sound stops. You can use a scope, I use a 2.5 VAC scale of an analog VOM. I put a .047 uf capacitor in series with the probe to analog ground to prevent response on DC sources. Analog VOM have no electrolytic caps to require replacement in 20 years. My Simpson 266XLPM meter was bought in 1987.
I use a cheap FM radio for a signal source, out the earphone jack. Turn down to 1/3 or less, earphones can go to 7 vac which is too much signal. If tuned to a rock station you can see the beats of the music on the meter probe. which looks nothing like ultrasonic oscillation, high & steady.
If you find a point that when you touch it it makes the sound flow, you've likely found the bad joint. So put the output to a amp+speaker while you probe.
When working a unit with the power on, wear no jewelry on hands or neck, 1 v at 50 amps can burn your flesh to charcoal. Use only one hand at a time, 25 v across your heart can stop it. Use an alligator clip lead for the ground probe. Wear safety glasses especially desoldering.
You poor Europeans and your hair. My native Am hair is permanent on my head, and not on my face or chest.
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Thanks for getting back indianajo!
Will be taking a much closer look at the pots and selector tho'...
Unfortunately...no scope, so this isn't a way forward for me!
Will be taking a much closer look at the pots and selector tho'...