Mark Bass TTE500 Schematic

[nickb]

I know it's long shot, but does anyone have any info on this horrid hybrid with 4 x 12A_7's and 18 x opamps in the signal path all **sigh**

[MarkusBass]

Are you sure that there are 18 opamps? I've seen a version with 9 opamps only. I was fixing the amp on which the owner spilled out a glass of beer. I failed to fix it and ended up ordering a new preamp board. The board is covered with silicone and it has a lot of vias. I could draw the schematic but I thought that it will take to much time so I ordered a new board.

Mark

[nickb]

Are you sure that there are 18 opamps? I've seen a version with 9 opamps only. I was fixing the amp on which the owner spilled out a glass of beer. I failed to fix it and ended up ordering a new preamp board. The board is covered with silicone and it has a lot of vias. I could draw the schematic but I thought that it will take to much time so I ordered a new board.

Mark

That is correct. But 9 dual packages = 18 op-amps

It's making that classic noisy component sound. Freezer spray doesn't help to localize. I've narrowed it down somewhat but insane amounts of silicone gloop covering every capacitor and also covering all the nearby surface mount components makes it very hard to know what connects to what. I'm gradually removing it but it's taking way too much time.

[MarkusBass]

If you count the opamps in this way, you should also specify 8 valves (because each of them is double triode).
I managed to remove the silicone but that didn't help.
I think that basic troubleshooting can be performed by removing each valve, one at a time. Do you have the noise on every output?

Mark

[nickb]

If you count the opamps in this way, you should also specify 8 valves (because each of them is double triode).
I managed to remove the silicone but that didn't help.
I think that basic troubleshooting can be performed by removing each valve, one at a time. Do you have the noise on every output?

Mark

I know, I'm just showing my bias

I've narrowed it down to before one tube and after the tone stack. It has a 33K grid to ground and a 100K feeding some part of the signal to it. If I ground the far side of the 100K the noise is not reduced. If I short the grid to ground noise is killed. It's not the tube in case you were wondering. So, I've replaced the 0805 sized 33k and the 100K (after removing yet more gloop) and it didn't help. Therefore, there must be another signal path coming into that node that, for the moment, I just can't see.

This is the sort of problem that would take 10 mins with a schematic.

[Enzo]

Tube is the part, triode is what is inside it. IC is the part, op amp is what is inside it. If we stick with that, we don;t get confused.

[MarkusBass]

Do you mean components between V3 and V4? If I were to guess, I would rather look at diodes on opamps inputs. For example, D17 and D18. Usually, failure of such a diode causes that amp is noisy. Do you have correct +/-15V rails?

Mark

[nickb]

Yes, those ones. Have you got one in front of you or do you have a photographic memory? I can't even remember what I had for breakfast...

[MarkusBass]

Yes, those ones. Have you got one in front of you or do you have a photographic memory?

I have the board somewhere around. I just thought that resistors cannot make the amp noisy - what would be the failure? Noise is rather caused by active circuits like tubes, opamps, diodes. Check voltages on "diode-protected" opamp inputs and on outputs. But be aware that some opamps in this preamp have DC voltage on the output because they are used for compression.

I can't even remember what I had for breakfast...

Let me remind you what you had. You had ......... English breakfast .

Mark

[Enzo]

Can't make it noisy? Resistors are one of the first things I suspect in a noisy tube stage. A quick tube swap to decide if the tube is noisy, then I go right to plate resistors.

Failure? Mechanical structure. Carbon grains that have loosened, crimped end contacts that have loosened. Adsorbed moisture inside teh resistance stuff. And so on.

[nickb]

I
Let me remind you what you had. You had ......... English breakfast .

Mark

Man , you're a genius, how did you know that!

[nickb]

Can't make it noisy? Resistors are one of the first things I suspect in a noisy tube stage. A quick tube swap to decide if the tube is noisy, then I go right to plate resistors.

Failure? Mechanical structure. Carbon grains that have loosened, crimped end contacts that have loosened. Adsorbed moisture inside teh resistance stuff. And so on.

Those are always my first suspects too. I got it done. In this case it was a ceramic cap.

[Enzo]

We have a local "Irish Pub", and they have "English Breakfast" on the menu. Has black and white puddings - like sausage - and sausage, and I forget what else. I always wondered if an Englishman came to visit, would he recognize it as a favorite from home. I grew up in MAryland, and I ate fried chicken all the time, but it wasn't until I moved to Michigan I heard of something called Maryland Fried Chicken. SOme friends of my sister had visitors from Ireland once, and bought some Irish Spring bath soap so they'd feel at home. Of course the Irish folks had never heard of that AMerican brand.

[nickb]

We have a local "Irish Pub", and they have "English Breakfast" on the menu. Has black and white puddings - like sausage - and sausage, and I forget what else. I always wondered if an Englishman came to visit, would he recognize it as a favorite from home. I grew up in MAryland, and I ate fried chicken all the time, but it wasn't until I moved to Michigan I heard of something called Maryland Fried Chicken. SOme friends of my sister had visitors from Ireland once, and bought some Irish Spring bath soap so they'd feel at home. Of course the Irish folks had never heard of that AMerican brand.

Black and white puddings are basically the same thing, i.e. oatmeal, except one is soaked in blood. I've never had that for breakfast. Tea and crumpets (covered in Marmite, naturally) is my stable.