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September 28, 2020, 04:58:04 PM

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91
Amplifier Discussion / Re: Trying To Repair a Traynor TBM 25...
« Last post by Enzo on August 20, 2020, 02:09:00 PM »
Perfectly normal for the two 330 ohm resistors to get hot.  Hopefully there is about 7.5v across each of the two diodes.

You say it sounds OK through headphones, but does it still sound OK through the phones with the speaker also connected?  Oh wait, you say the phones makes the speaker silent?  The schematic does not show a cutout, but we can deal.  With speaker connected, how does the line out sound?  Run that to some other amp.  Does the line out sound change when speaker is connected or removed.

You soldered some stuff and it came to life then failed again.  SOunds like you have a bad connection or cracked copper trace somewhere.  Not so much a bad part.  Transistors don't generally die and heal themselves.
92
Amplifier Discussion / Re: fender ultra chorus distortion
« Last post by g1 on August 20, 2020, 01:58:03 PM »
Schematic shows VDD pins of chorus chips going to ground.
Tough to say if that's the only error in the chorus part of schematic.
If schematic is wrong, that's not going to help.  :(

(edit: my error, schematic is correct)
93
Amplifier Discussion / Re: fender ultra chorus distortion
« Last post by ilyaa on August 20, 2020, 01:22:37 PM »
No dice -

U6 replaced, Q6 and Q7 replaced, C41 and C42 replaced, C89 and C88 replaces -

No change - man what is behind this?

The reason I suspect the effect itself is that if I turn the chorus trim pot I can hear the distortion getting worse as i turn it away from the center position in either direction -
94
Amplifier Discussion / Re: Trying To Repair a Traynor TBM 25...
« Last post by debrad on August 20, 2020, 11:44:27 AM »
Q does the speaker switch off when you insert the headphones?
Phil.

Yes...the speaker is silent when headphones are plugged into the jack.  The other day I removed the jack entirely, soldered a jumper to make the output connection to the speaker leads, and it was still muddy, distorted, and low volume so the switching jack doesn't appear to be the problem.

With the jack in place, the speaker output is so poor and yet the exact same output running into headphones is so loud and clear.

FYI, the output at the "Line Out" jack sounds just like the speaker...muddy, distorted, and low volume.

95
Amplifier Discussion / Re: Trying To Repair a Traynor TBM 25...
« Last post by phatt on August 20, 2020, 08:46:13 AM »
Q does the speaker switch off when you insert the headphones?
Phil.
96
Amplifier Discussion / Trying To Repair a Traynor TBM 25...
« Last post by debrad on August 20, 2020, 01:24:28 AM »
Hi everyone,

First, thanks for allowing me to join you here.  I have done a lot of fx pedal building and recently completed the conversion of a Filmosound tube-based projector amp but a friend just asked me to look into his SS Traynor amp and it's the first time I have worked with one.

The basic issue is reduced output with a muddy tone and plenty of distortion through the speaker but loud clean output through the headphone jack.  I have verified that the speaker works fine by playing my Traynor YCV40 through it and, thanks to some suggestions on a SS Facebook page, I have also confirmed that the headphone switch/jack is working and that the DC offset is about 6mV.

Last night I found several pads on the PCB that were damaged or broken so I fixed and/or jumpered those and reflowed the solder on EVERY connection.  Low and behold, the speaker output was great for about 5 minutes of testing and then it abruptly switched back to the low mud and distortion.

One of the Facebook members suggested a test of the output transistors and I noticed that the 2 watt 330 ohm resistors and their adjacent diodes get very hot VERY fast and have actually discoloured/burned the PCB around them.  In addition, a light tap on those resistors with a wooden stick also caused a bit of the surface to flake off.

Now, I noticed another member was having heat issues with his TBM-25 and that was another reason why I requested to join this group since I figured he must have gotten those sorted out with your help.

I can attach a copy of the Traynor schematic for this amp once I figure out how to upload a PDF and I am hoping that you might be able to help point me towards a solution to this problem.  In the meantime, I *HOPE* the schematic is still available from the forum post here:

https://www.ssguitar.com/index.php?topic=4354.msg34812#msg34812

I look forward to your replies and thank you in advance!


- brad -
97
Amplifier Discussion / Re: fender ultra chorus distortion
« Last post by Enzo on August 19, 2020, 04:52:16 PM »
Look at the data sheet for the 3101, note it runs on -16v, that is a negative supply.  SO if they connect +15 to ground and ground to the VDD terminal, the IC sees a negative supply.   The VDD terminal is 15v more negative than the +15 supply.

Your MN chips are probably fine.   Remember the chorus circuit path is a lot more than the MN chips.  Certainly U6, and Q6 could be leaky as well.
98
Amplifier Discussion / Re: fender ultra chorus distortion
« Last post by ilyaa on August 19, 2020, 02:32:17 PM »
Haven’t found any similar complaints -

I’m not too familiar with chorus chips - here is what seems odd maybe:

The P-P square at pins 2 and 4 of the 3101 and 2 and 6 of the 3007 should be like 15V peak to peak but it’s more like 30V peak to peak -

I’ve got about 1VDC at pin 8 of the 3101 at pin 4 of them 3007. That ok?

It’s confusing because data sheet says pin 8 should be 14/15 of pin 3, but pins 1 and 3 are swapped in this design - with 1 being the supply instead of ground and vice versa with 3....

And at pin 5 and 6 - the input of the 3101 - there is some weird looking oscillation - but thats supposed to be there according to data sheet

Oh, and no noticeable ripple of low voltage rails

This whole thing feels like I’m barking up the wrong tree - but this noise is def chord related and it’s def bad!
99
Amplifier Discussion / Re: fender ultra chorus distortion
« Last post by joecool85 on August 18, 2020, 09:23:10 PM »
The +/- 18 sounds a bit high for 16V zeners.  Check for ripple on those supply rails.
Also, the schematic does not seem to show where the 3007 & 3101 get their supply from.  Check for ripple on those supply pins too.

Is it possible that this is normal for this model?  It sounds like there is no problem unless the chorus chips get too large of a signal?  You might want to check around and see if other people have complained about this issue for the same model.

If all checks out but this is just poor design, he could always do a voltage divider running into the chorus circuit so that it didn't get quite so hot a signal.
100
Amplifier Discussion / Re: fender ultra chorus distortion
« Last post by g1 on August 18, 2020, 08:57:44 PM »
The +/- 18 sounds a bit high for 16V zeners.  Check for ripple on those supply rails.
Also, the schematic does not seem to show where the 3007 & 3101 get their supply from.  Check for ripple on those supply pins too.

Is it possible that this is normal for this model?  It sounds like there is no problem unless the chorus chips get too large of a signal?  You might want to check around and see if other people have complained about this issue for the same model.
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