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Wurlitzer 1600 (518 amp) low volume



 
 
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  #1  
Old May 10th 04, 07:26 PM
Jonathan Day
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Default Wurlitzer 1600 (518 amp) low volume

I am in the process of restoring a Wurlitzer 1600 with a model 518
amp. I re-capped the amp and replaced all resistors that had drifted
out of tolerence. All tubes checked good with the exception of the
6J5 and 6L6's which have been replaced. All voltages checked within
10% of the values shown on the schematic.

The problem is that the volume of the amp is quite low. At max
volume, it is at about 1/2 the level that it should be. There is no
audible sound at all until the volume control is at about the half-way
position. There is no hum or distortion in the sound, it is just too
low.

I have tried the following:
I have 4 different cobra cartridges and all sound the same.
I have a spare set of tubes and replacing any or all of them makes no
difference.
Unplugging either of the output tubes makes no difference in sound
output. In other words it doesn't matter which tube is removed, the
output level is the same. Obviously, however, removing both tubes
results no sound at all.


Any ideas? I'm really stumped on this one.

Thanks,
Jonathan
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  #2  
Old May 10th 04, 09:38 PM
John Robertson
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Posts: n/a
Default

Perhaps you made a mistake when you recapped the amp? Verify each
value and that you didn't accidentally connect one to ground or short
one of the pass capacitors to ground or the wrong circuit.

John :-#)#

On 10 May 2004 11:26:59 -0700, (Jonathan Day)
wrote:

I am in the process of restoring a Wurlitzer 1600 with a model 518
amp. I re-capped the amp and replaced all resistors that had drifted
out of tolerence. All tubes checked good with the exception of the
6J5 and 6L6's which have been replaced. All voltages checked within
10% of the values shown on the schematic.

The problem is that the volume of the amp is quite low. At max
volume, it is at about 1/2 the level that it should be. There is no
audible sound at all until the volume control is at about the half-way
position. There is no hum or distortion in the sound, it is just too
low.

I have tried the following:
I have 4 different cobra cartridges and all sound the same.
I have a spare set of tubes and replacing any or all of them makes no
difference.
Unplugging either of the output tubes makes no difference in sound
output. In other words it doesn't matter which tube is removed, the
output level is the same. Obviously, however, removing both tubes
results no sound at all.


Any ideas? I'm really stumped on this one.

Thanks,
Jonathan


(Please post followups or tech enquires to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

  #3  
Old May 11th 04, 03:33 PM
Ken Layton
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Posts: n/a
Default

Sounds like a bad cathode bypass electrolytic cap in the front end of the amp.
  #4  
Old May 11th 04, 10:16 PM
Dirt poor John
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Posts: n/a
Default

How about the mute switch ? I recently had a Wurlitzer 1700 with a broken
switch held in the closed position AND corroded contacts. This gave the
same type problem you are having with yours.

DPJ


"Jonathan Day" wrote in message
om...
I am in the process of restoring a Wurlitzer 1600 with a model 518
amp. I re-capped the amp and replaced all resistors that had drifted
out of tolerence. All tubes checked good with the exception of the
6J5 and 6L6's which have been replaced. All voltages checked within
10% of the values shown on the schematic.

The problem is that the volume of the amp is quite low. At max
volume, it is at about 1/2 the level that it should be. There is no
audible sound at all until the volume control is at about the half-way
position. There is no hum or distortion in the sound, it is just too
low.

I have tried the following:
I have 4 different cobra cartridges and all sound the same.
I have a spare set of tubes and replacing any or all of them makes no
difference.
Unplugging either of the output tubes makes no difference in sound
output. In other words it doesn't matter which tube is removed, the
output level is the same. Obviously, however, removing both tubes
results no sound at all.


Any ideas? I'm really stumped on this one.

Thanks,
Jonathan



  #5  
Old May 19th 04, 02:17 PM
Jonathan Day
external usenet poster
 
Posts: n/a
Default

Thanks for all the input, guys. I found that the lower tonearm plays
at a much higher volume than the upper tonearm. I eliminated the
switch that connects the correct tonearm to the main input cable via a
jumper, so it looks like my problem is with the wiring between the
upper tonearm and the switch. I would prefer to change the all the
cables between the tonearms and the amp, but all of the shielded
cables that I have around the shop introduce a very loud hum. Is
there something special about the cable since this box uses a cobra
cartridge? Has anyone found a suitable replacement for the heavy
cable that goes to the amp as well as the smaller wires that connect
to the cartridge?

Thanks,
Jonathan

(Jonathan Day) wrote in message . com...
I am in the process of restoring a Wurlitzer 1600 with a model 518
amp. I re-capped the amp and replaced all resistors that had drifted
out of tolerence. All tubes checked good with the exception of the
6J5 and 6L6's which have been replaced. All voltages checked within
10% of the values shown on the schematic.

The problem is that the volume of the amp is quite low. At max
volume, it is at about 1/2 the level that it should be. There is no
audible sound at all until the volume control is at about the half-way
position. There is no hum or distortion in the sound, it is just too
low.

I have tried the following:
I have 4 different cobra cartridges and all sound the same.
I have a spare set of tubes and replacing any or all of them makes no
difference.
Unplugging either of the output tubes makes no difference in sound
output. In other words it doesn't matter which tube is removed, the
output level is the same. Obviously, however, removing both tubes
results no sound at all.


Any ideas? I'm really stumped on this one.

Thanks,
Jonathan

 




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