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1988 Fender Princeton Chorus amp...

S

server

Guest
Hello, I have a 1988 Fender Princeton Chorus amp, I believe this was the first year model.

I have a faint chorus sound/FX in both the rate & the depth controls.

I replaced the MN 3007 & MN 3001 chips today, but still no real change. The chorus FX is there, but really faint.

Both speakers are working, both sides of the amp seem to be working and the amp is totally stock. Nobody
has changed anything except for what I did today.

Can you help me ? Maybe tell me what else to change ?

I can’t read a schematic at all, so please if you could be so kind, please explain where to find the parts that
you might suggest that I try changing.

Stay safe, Charles

NOTE: I live at least 200 miles from the nearest repair station so I\'d really like to fix this problem myself with your help of course :)
 
P

Pimpom

Guest
On 7/16/2020 11:23 AM, cvalona09@gmail.com wrote:
Hello, I have a 1988 Fender Princeton Chorus amp, I believe this was the first year model.

I have a faint chorus sound/FX in both the rate & the depth controls.

I replaced the MN 3007 & MN 3001 chips today, but still no real change. The chorus FX is there, but really faint.

Both speakers are working, both sides of the amp seem to be working and the amp is totally stock. Nobody
has changed anything except for what I did today.

Can you help me ? Maybe tell me what else to change ?

I can’t read a schematic at all, so please if you could be so kind, please explain where to find the parts that
you might suggest that I try changing.

Stay safe, Charles

NOTE: I live at least 200 miles from the nearest repair station so I\'d really like to fix this problem myself with your help of course :)
Can you post a link to the schematic? This will help others help
you even if you can\'t read it yourself. The exact model number
and a photo will also be helpful.
 
A

abrsvc

Guest
None of the Princeton models that I found have the chips you describe. Can you post the exact model from the plate? The only Princeton Chorus model I found has DSP in the model name as well.

I have some hardcopy schematics around that I will check as well, but any additional info you can provide will help.

Dan
 
P

Pimpom

Guest
On 7/16/2020 5:35 PM, abrsvc wrote:
None of the Princeton models that I found have the chips you describe. Can you post the exact model from the plate? The only Princeton Chorus model I found has DSP in the model name as well.
Same here. That\'s why I asked the OP to provide more details. I
couldn\'t find any model using a BBD.
 
A

abrsvc

Guest
Without the schematic, based upon the symptoms described:

1) The \"delay\" portion is working as expected
2) The delayed signal amplitude is smaller than expected. This would suggest that there is likely an op-amp down stream that is not working correctly or at all. Look for a TC072 or perhaps a 4558 IC that is faulty post the MN chips.

Dan
 
W

Wond

Guest
On Thu, 16 Jul 2020 06:45:11 -0700, abrsvc wrote:

Without the schematic, based upon the symptoms described:

1) The \"delay\" portion is working as expected 2) The delayed signal
amplitude is smaller than expected. This would suggest that there is
likely an op-amp down stream that is not working correctly or at all.
Look for a TC072 or perhaps a 4558 IC that is faulty post the MN chips.

Dan
Or high ESR coupling cap?
 
A

abrsvc

Guest
None of the Princeton models that I found have the chips you describe. Can you post the exact model from the plate? The only Princeton Chorus model I found has DSP in the model name as well.

I have some hardcopy schematics around that I will check as well, but any additional info you can provide will help.

Dan
 
P

Phil Allison

Guest
abrsvc wrote:

=============
None of the Princeton models that I found have the chips you describe.
----------------------------

See:

http://www.kobra.hr/Schematics/Chorus/Fender%20Princeton%20%20Stereo%20Chorus.jpg


The repair is a job for an experienced amp tech with the usual test gear on hand - scope, audio gen etc.



..... Phil
 
P

Phil Allison

Guest
abrsvc wrote:

=============
None of the Princeton models that I found have the chips you describe.
----------------------------

See:

http://www.kobra.hr/Schematics/Chorus/Fender%20Princeton%20%20Stereo%20Chorus.jpg


The repair is a job for an experienced amp tech with the usual test gear on hand - scope, audio gen etc.



..... Phil
 
S

server

Guest
On Wednesday, July 15, 2020 at 10:53:29 PM UTC-7, cval...@gmail.com wrote:
Hello, I have a 1988 Fender Princeton Chorus amp, I believe this was the first year model.

I have a faint chorus sound/FX in both the rate & the depth controls.

I replaced the MN 3007 & MN 3001 chips today, but still no real change. The chorus FX is there, but really faint.

Both speakers are working, both sides of the amp seem to be working and the amp is totally stock. Nobody
has changed anything except for what I did today.

Can you help me ? Maybe tell me what else to change ?

I can’t read a schematic at all, so please if you could be so kind, please explain where to find the parts that
you might suggest that I try changing.

Stay safe, Charles

NOTE: I live at least 200 miles from the nearest repair station so I\'d really like to fix this problem myself with your help of course :)
 
S

server

Guest
On Wednesday, July 15, 2020 at 10:53:29 PM UTC-7, cval...@gmail.com wrote:
Hello, I have a 1988 Fender Princeton Chorus amp, I believe this was the first year model.

I have a faint chorus sound/FX in both the rate & the depth controls.

I replaced the MN 3007 & MN 3001 chips today, but still no real change. The chorus FX is there, but really faint.

Both speakers are working, both sides of the amp seem to be working and the amp is totally stock. Nobody
has changed anything except for what I did today.

Can you help me ? Maybe tell me what else to change ?

I can’t read a schematic at all, so please if you could be so kind, please explain where to find the parts that
you might suggest that I try changing.

Stay safe, Charles

NOTE: I live at least 200 miles from the nearest repair station so I\'d really like to fix this problem myself with your help of course :)
Thanks for your help everyone, however, the IC\'s MN 3101 and MN 3007 are stock parts that came out of my completely stock virgin 1988 Solid State Fender Princeton Chorus amp. Not sure why you\'re not seeing them ?
 
S

server

Guest
On Wednesday, July 15, 2020 at 10:53:29 PM UTC-7, cval...@gmail.com wrote:
Hello, I have a 1988 Fender Princeton Chorus amp, I believe this was the first year model.

I have a faint chorus sound/FX in both the rate & the depth controls.

I replaced the MN 3007 & MN 3001 chips today, but still no real change. The chorus FX is there, but really faint.

Both speakers are working, both sides of the amp seem to be working and the amp is totally stock. Nobody
has changed anything except for what I did today.

Can you help me ? Maybe tell me what else to change ?

I can’t read a schematic at all, so please if you could be so kind, please explain where to find the parts that
you might suggest that I try changing.

Stay safe, Charles

NOTE: I live at least 200 miles from the nearest repair station so I\'d really like to fix this problem myself with your help of course :)
Thanks for your help everyone, however, the IC\'s MN 3101 and MN 3007 are stock parts that came out of my completely stock virgin 1988 Solid State Fender Princeton Chorus amp. Not sure why you\'re not seeing them ?
 
S

server

Guest
On Wednesday, July 15, 2020 at 10:53:29 PM UTC-7, cval...@gmail.com wrote:
Hello, I have a 1988 Fender Princeton Chorus amp, I believe this was the first year model.

I have a faint chorus sound/FX in both the rate & the depth controls.

I replaced the MN 3007 & MN 3001 chips today, but still no real change. The chorus FX is there, but really faint.

Both speakers are working, both sides of the amp seem to be working and the amp is totally stock. Nobody
has changed anything except for what I did today.

Can you help me ? Maybe tell me what else to change ?

I can’t read a schematic at all, so please if you could be so kind, please explain where to find the parts that
you might suggest that I try changing.

Stay safe, Charles

NOTE: I live at least 200 miles from the nearest repair station so I\'d really like to fix this problem myself with your help of course :)
 
S

server

Guest
On Wednesday, July 15, 2020 at 10:53:29 PM UTC-7, cval...@gmail.com wrote:
Hello, I have a 1988 Fender Princeton Chorus amp, I believe this was the first year model.

I have a faint chorus sound/FX in both the rate & the depth controls.

I replaced the MN 3007 & MN 3001 chips today, but still no real change. The chorus FX is there, but really faint.

Both speakers are working, both sides of the amp seem to be working and the amp is totally stock. Nobody
has changed anything except for what I did today.

Can you help me ? Maybe tell me what else to change ?

I can’t read a schematic at all, so please if you could be so kind, please explain where to find the parts that
you might suggest that I try changing.

Stay safe, Charles

NOTE: I live at least 200 miles from the nearest repair station so I\'d really like to fix this problem myself with your help of course :)
 
S

server

Guest
On Thursday, July 16, 2020 at 5:05:30 AM UTC-7, abrsvc wrote:
None of the Princeton models that I found have the chips you describe. Can you post the exact model from the plate? The only Princeton Chorus model I found has DSP in the model name as well.

I have some hardcopy schematics around that I will check as well, but any additional info you can provide will help.

Dan
Thanks Dan,

My 1988 Fender Princeton Chorus Model PR82 Made In USA is completely stock, a totally virgin amp. The IC\'s MN 3101 and MN 3007 are stock parts that came out of this amp. I replaced them with new ones yesterday, but no change, the Chorus is still having problems. The pilot light comes on, and both the Rate & Depth controls seem to be working, but the FX is very very weak.

BTW...this is not a Princeton that uses DSP...the amps that featured DSp effects came after the PR82 models and don\'t sound near as good.

Stay Safe, Charles
 
S

server

Guest
On Thursday, July 16, 2020 at 2:52:19 PM UTC-7, Phil Allison wrote:
abrsvc wrote:

=============

None of the Princeton models that I found have the chips you describe.


----------------------------

See:

http://www.kobra.hr/Schematics/Chorus/Fender%20Princeton%20%20Stereo%20Chorus.jpg


The repair is a job for an experienced amp tech with the usual test gear on hand - scope, audio gen etc.



.... Phil
 
S

server

Guest
On Wednesday, July 15, 2020 at 10:53:29 PM UTC-7, cval...@gmail.com wrote:
Hello, I have a 1988 Fender Princeton Chorus amp, I believe this was the first year model.

I have a faint chorus sound/FX in both the rate & the depth controls.

I replaced the MN 3007 & MN 3001 chips today, but still no real change. The chorus FX is there, but really faint.

Both speakers are working, both sides of the amp seem to be working and the amp is totally stock. Nobody
has changed anything except for what I did today.

Can you help me ? Maybe tell me what else to change ?

I can’t read a schematic at all, so please if you could be so kind, please explain where to find the parts that
you might suggest that I try changing.

Stay safe, Charles

NOTE: I live at least 200 miles from the nearest repair station so I\'d really like to fix this problem myself with your help of course :)
 
S

server

Guest
On Wednesday, July 15, 2020 at 10:53:29 PM UTC-7, cval...@gmail.com wrote:
Hello, I have a 1988 Fender Princeton Chorus amp, I believe this was the first year model.

I have a faint chorus sound/FX in both the rate & the depth controls.

I replaced the MN 3007 & MN 3001 chips today, but still no real change. The chorus FX is there, but really faint.

Both speakers are working, both sides of the amp seem to be working and the amp is totally stock. Nobody
has changed anything except for what I did today.

Can you help me ? Maybe tell me what else to change ?

I can’t read a schematic at all, so please if you could be so kind, please explain where to find the parts that
you might suggest that I try changing.

Stay safe, Charles

NOTE: I live at least 200 miles from the nearest repair station so I\'d really like to fix this problem myself with your help of course :)
My 1988 Fender Princeton Chorus Model PR82 Made In USA is completely stock, a totally virgin amp. The IC\'s MN 3101 and MN 3007 are stock parts that came out of this amp. I replaced them with new ones yesterday, but no change, the Chorus is still having problems. The pilot light comes on, and both the Rate & Depth controls seem to be working, but the FX is very very weak.

BTW...this is not a Princeton that uses DSP...the amps that featured DSp effects came after the PR82 models and don\'t sound near as good.

Stay Safe, Charles
 
S

server

Guest
On Thursday, July 16, 2020 at 5:05:30 AM UTC-7, abrsvc wrote:
None of the Princeton models that I found have the chips you describe. Can you post the exact model from the plate? The only Princeton Chorus model I found has DSP in the model name as well.

I have some hardcopy schematics around that I will check as well, but any additional info you can provide will help.

Dan
Thanks Dan,

My 1988 Fender Princeton Chorus Model PR82 Made In USA is completely stock, a totally virgin amp. The IC\'s MN 3101 and MN 3007 are stock parts that came out of this amp. I replaced them with new ones yesterday, but no change, the Chorus is still having problems. The pilot light comes on, and both the Rate & Depth controls seem to be working, but the FX is very very weak.

BTW...this is not a Princeton that uses DSP...the amps that featured DSp effects came after the PR82 models and don\'t sound near as good.

Stay Safe, Charles
 
J

Jeff Urban

Guest
First of all Phil is probably right. But then if you want to try things on your own...

The chips you mentioned are probably the clock and BBD. They really should not affect the level of sound.

Turn the chorus off and see if you are getting the same volume out of each speaker.

If the sound is equal then you need to go right after the BBD circuit. If not it could be in the amp on that side anywhere.
 
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