Collins Radio 26U-1 limiter restoration and modification

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emrr

Well-known member
Joined
Apr 12, 2006
Messages
8,525
Location
NC, USA
Here's one I just finished for a client.  These pics chart the progress.  Looked like it had lived in a barn for awhile; had mud dauber nest residue inside.  He wanted modern connectors on the back and more controls on the front, so here's what I came up with.  All new caps, several of the PSU resistances were broken, or way off.  Note on these that the door support on the right side is extremely close to the rectifier(!), and if bent incorrectly, will make a shorting contact when the door is shut.  I am not a fan of these particular Daven input and output ladders, as they are the only Daven types you cannot easily open and clean.  Not sure why they were used here. 

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The dots at the attack and release pots mark original slowest attack and fastest release.  The ratios are simply taps on the side chain bias voltage divider, and were plotted using the method described in the manual, which is available online.  Note the GR meter marking is only really (kind of) accurate at the stock ratio (highest), and with steady state tones.  If you compare the meter markings with the markings for the 26J/356E compressor (find and see manual) you will see the difference for the lower ratios.  These sorts of meters give more of an idea of action, versus actual specific information. 

3384657239_1a6cb81d6e_b.jpg


 
EmRR said:
Here's one I just finished for a client.  These pics chart the progress.  Looked like it had lived in a barn for awhile; had mud dauber nest residue inside.  He wanted modern connectors on the back and more controls on the front, so here's what I came up with.  All new caps, several of the PSU resistances were broken, or way off.  Note on these that the door support on the right side is extremely close to the rectifier(!), and if bent incorrectly, will make a shorting contact when the door is shut.  I am not a fan of these particular Daven input and output ladders, as they are the only Daven types you cannot easily open and clean.  Not sure why they were used here. 

3385456942_c7fbb0d731_b.jpg


3385493742_8c15e6b8a7_b.jpg


3385458900_c4b8a18409_b.jpg


3384623025_d8ed55e435_b.jpg


3384625191_2cf0b4b50e_b.jpg


3384653089_043a4f6d9b_b.jpg


3385465378_3366d078a1_b.jpg


3385445726_1479c611f5_b.jpg


The dots at the attack and release pots mark original slowest attack and fastest release.  The ratios are simply taps on the side chain bias voltage divider, and were plotted using the method described in the manual, which is available online.  Note the GR meter marking is only really (kind of) accurate at the stock ratio (highest), and with steady state tones.  If you compare the meter markings with the markings for the 26J/356E compressor (find and see manual) you will see the difference for the lower ratios.  These sorts of meters give more of an idea of action, versus actual specific information. 

3384657239_1a6cb81d6e_b.jpg

Dear EmRR,

I have the same unit but without power transformer and I have open another post with this information petition with any positive result!.

Do you have any information about of this power transformer? or do you know a substitution for that?

Thanks a lot anticipated
opacheco
 

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