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Jordan Two/01 Repair

Started by cdparady, December 06, 2022, 06:03:06 PM

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cdparady

Thought I would start a fresh thread on this, I posted looking for a schematic a few weeks back.

Just getting into the amp, here are a few starting notes & pics.....
 
- Speaker cabinet long gone
- No schematic in the cabinet, but bonus on the wiring diagram (pic below)
- 2 TO3 Outputs ECG210/ECG181
- Amp board looks toasty, other boards in great condition
- Death Cap Still in Place (!!)

I will add some additional photos as I progress, goal is to get it cleaned up, operational & safe.

Thx, Chris

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Tassieviking

That power amp PCB could do with some flux remover.
It would be a fun amp to trace out the schematic from the PCB's.
If you take a photo of the PCB with a bright light on the opposite side it should not be too hard.
There are no stupid questions.
There are only stupid mistakes.

cdparady

Update - Couple of additional pictures of the amp board cleaned up.

- Amp is Dual Rail +/- 30 VDC
- I believe Class AB 
- Looks like one pre-driver replaced in the past

More to follow.....

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cdparady

One more update for today....AC Power Cleaned Up

- Death Cap Removed
- New 3 Wire Grounded Cord
- New Fuse Holder
- New Power Switch

Note, accessory outlet was shaky, gutted it and bypassed it.

Made some progress on the amp board, will post another update in the next few days.

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dmeek

Are there any numbers on those 4 transistors? The blue 1000uf cap seems to be reversed.You cannot view this attachment.

cdparady

LOL that someone noticed the cap polarity ..... !!

It was definitely in backward from the factory, silkscreen wrong, factory install wrong.   Corrected it on the new install.

Transistor details coming on the next post.

cdparady

Update #2 - Worked through the amp board last week......

Testing Notes:

- Output clipping 1/2 way through the negative cycle
- DC Offset -6VDC
- Signs of prior repair, one pre-driver replaced at some point and at least one diode
- ECG181 (PNP) Running Hot At Idle

Repairs:

- Filter Caps & Drivers Tested OK
- Replaced Input Cap & The -9VDC Electrolytic (Note "+" Sign Silk Screen Wrong on Board)
- Bridge Diodes Tested Fine, Replaced 5 Others
- Several of the small TO92's tested bad, so I swapped them all out
- Pre-drivers were unmatched from prior repairs, replaced with higher power MJE TO225's
- Details Attached on all of the components, originals, pin outs, replacements

One important note, the right side of the board (bottom view) near the -9VDC pins to the pre-amp boards and tremolo/reverb board does not share a common ground trace with the left side of the board....the return path is through the chassis.  Whether that was a intentional design or not, who knows.  That was the root cause of the DC offset issue, bad ground.

Final Test:

- Board came back up in very nice shape, scope trace attached
- Measured 16 VAC RMS just before clipping into an 8 Ohm Load, so 32 Watts RMS
- DC Offset Settled in at about 250 mV DC
- Both Preamp Boards Tested Fine
- Tremolo Tested OK, Reverb Tank long gone so no Reverb

Will post pics of the preamp boards (both the same) and the Tremlo/Reverb board.

Happy reading !

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- Power Transistors, Main Filter Caps
-

cdparady

Update #3 - Preamp & Tremolo/Reverb Boards

Board Location - Tremolo/Reverb Board Top, Preamps Middle & Bottom

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Tremolo/Reverb Board

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Preamp Boards (Identical)

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cdparady

Update #4 - Final Update

Final product, rebuilt the cabinet to look somewhat respectable !!

If anyone reverse engineers the schematic, please post !!

Merry Christmas all.

Chris P.

PS - For you OCD folks like me, bottom fully vented, replacement knob coming, owner is going to paint ;)

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dmeek

Here is the schematic of the power amp board. I believe it is correct but there could be mistakes.
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dmeek

Here is the input schematic. Please post another photo of the tremolo-reverb board.
I can't see the circled area very well.
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cdparady

Tremolo/Reverb Board Details

Here are some pics that should help .....

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dmeek

Here is the Tremolo-Reverb board
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joecool85

Awesome job @cdparody and @dmeek!
Life is what you make it.
Still rockin' the Dean Markley K-20X
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