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Post subject: Blues Deluxe Reissue channel switching/reverb issue
Posted: Fri Nov 02, 2012 9:22 am
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Hello all, I am looking for some help diagnosing a channel select/reverb problem. I checked all my Test Points (30-36) and can't seem to understand where my problem lies.
Here are some of the voltages:
TP30
-14v steady
+16v channel change

TP31
nominal voltages

TP32
+16v drive channel selected (supposed to be -16v!!!!)
+16v normal channel (supposed to be +7.5v)

TP33
nominal voltages

TP34
+.082v reverb off
-17.43v reverb on (supposed to be -1.38v)

TP35
+.7v off
-33.1 v on (supposed to be -2.2v!!!!! Blown Diode????)

TP36
16.35 v off
16.33v on (supposed to be -15.6v!!!!!)

Also K1 is ticking when I select drive channel and the reverb is on with footswitch plugged in.

With footswitch unplugged. Only drive channel has reverb. No reverb on the clean channel at all!

Checked +16v/-16v supply and it checks good.

Checked the 5watt resistors and they appear to be good.

Reflowed all joints on board.

Help!!!!!!!!!!!!!!
thanks


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Post subject: Re: Blues Deluxe Reissue channel switching/reverb issue
Posted: Fri Nov 02, 2012 9:40 am
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Relay K1 is suspect -- recommend replacement.

HTH

Arjay

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Post subject: Re: Blues Deluxe Reissue channel switching/reverb issue
Posted: Fri Nov 02, 2012 10:51 am
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Actually, K2A is the relay that selects and sends either the clean or drive channel to the reverb circuit, so if you are only getting reverb on the drive channel, I would look at K2.

http://support.fender.com/schematics/gu ... _Rev-A.pdf

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Post subject: Re: Blues Deluxe Reissue channel switching/reverb issue
Posted: Fri Nov 02, 2012 10:55 am
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Funky voltages on K1, so I replaced it. No more relentless ticking. But still no verb on clean channel. So I will try K2. Thanks! Really driving me crazy!!!


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Post subject: Re: Blues Deluxe Reissue channel switching/reverb issue
Posted: Fri Nov 02, 2012 11:02 am
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Also the reverb led indicator on the footswitch works but the channel led does not even though it still switches channels. When Clean channel is selected and reverb is engaged, there is no audible signal through amp.

On a side note. I just recapped it with a fromel kit and this the 8th one I've done. Never had any trouble before. All caps are solid and polarized properly!

What gives?????!!!!!


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Post subject: Re: Blues Deluxe Reissue channel switching/reverb issue
Posted: Fri Nov 02, 2012 11:11 am
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Were any of these symptoms present prior to the re-cap?

Arjay

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Post subject: Re: Blues Deluxe Reissue channel switching/reverb issue
Posted: Fri Nov 02, 2012 11:25 am
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according to the owner. No


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Post subject: Re: Blues Deluxe Reissue channel switching/reverb issue
Posted: Fri Nov 02, 2012 11:37 am
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In all candor, you seem to know your way around an amp chassis.

Any chance your client is trying to pull a fast one by not informing you of other problems with the amp prior to servicing?

Arjay

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Post subject: Re: Blues Deluxe Reissue channel switching/reverb issue
Posted: Fri Nov 02, 2012 12:15 pm
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goldstache wrote:
Also the reverb led indicator on the footswitch works but the channel led does not even though it still switches channels. When Clean channel is selected and reverb is engaged, there is no audible signal through amp.

On a side note. I just recapped it with a fromel kit and this the 8th one I've done. Never had any trouble before. All caps are solid and polarized properly!

What gives?????!!!!!


Are you referring to the channel indicator on the footswitch or the amp? In either case, it could be something as simple as a bad LED. Since reverb works with the drive channel and not the clean channel, I think K2 should be your next area of concentration.

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Post subject: Re: Blues Deluxe Reissue channel switching/reverb issue
Posted: Fri Nov 02, 2012 3:21 pm
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Interesting. If you look closely at the circuit, K2A feeds the reverb and the PI (as well as K2B bypassing the drive pot), as the reverb is parallel to the main signal. I would think that if K2 was the problem, there would be no sound at all when switching channels. Although K1 was ticking, that seems to have been a symptom and not the cause.

After looking at the TP readings posted by the OP, the op amp U3 was the first thing that came to my mind, because it is common to the reverb and channels switching, and the wonky readings are on the output of both halves of that op amp.

Just another thought anyway. :idea:

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Last edited by shimmilou on Fri Nov 02, 2012 3:24 pm, edited 1 time in total.

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Post subject: Re: Blues Deluxe Reissue channel switching/reverb issue
Posted: Fri Nov 02, 2012 3:23 pm
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shimmilou wrote:
After looking at the TP readings posted by the OP, the op amp U3 was the first thing that came to my mind, because it is common to the reverb and channels switching, and the wonky readings are on the output of both halves of that op amp.


+1

Either half of U3 (if wonky) could play a part in the issue.

Arjay

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Post subject: Re: Blues Deluxe Reissue channel switching/reverb issue
Posted: Fri Nov 02, 2012 3:35 pm
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I would also double-check resistors R84 (330 ohm) and R104 (390 ohm), as well as their solder joints, both are in the circuit for U3 and relays. If TP33 checks out, and TP32 is incorrect, these two resistors are between those two TPs. If one of these two resistors were open (or broken solder joint or trace), I would expect to see +16 volts at TP32, as the +16 volt supply would be read through the relay coils.

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Post subject: Re: Blues Deluxe Reissue channel switching/reverb issue
Posted: Sat Nov 03, 2012 6:08 am
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Good stuff here! I take a look around and report back. Thanks for the help and insight!


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Post subject: Re: Blues Deluxe Reissue channel switching/reverb issue
Posted: Mon Nov 05, 2012 10:24 pm
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So I replaced U3, K1, and K2. Without footswitch plugged in, I finally have reverb on both channels, and channels switch cleanly. However with footswitch plugged in, reverb operates. But channel selection only clean works. The dirt channel is silent. I suppose it's in the mute section of the amp. Also the status led on the amp dims when clean(not fully off). Cant figure out why it only operates this way when the footswitch/relay section of the amp is in use!!!! STILL DIGGING......... Any further suggestions?????? Thanks you have all been a big help!!!!


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Post subject: Re: Blues Deluxe Reissue channel switching/reverb issue
Posted: Mon Nov 05, 2012 11:17 pm
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If the channel switching and reverb work fine without the foot switch, the foot switch, or cable is suspect. The mute section of the amp works the same with or without the foot switch.

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