Electronic DIY Project Troubleshooting Assistance

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#1263615 19-Mar-2015 18:22

Manuals will not help, the issue is with the assembly itself. Someone would need to check it out. Where in the country are you?

You can never have enough Volvos!

networkn

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#1263616 19-Mar-2015 18:25

SepticSceptic:
Niel: Each valve has 2 channels. You can't physically turn the valves around, but you can swap wires on the valve so that a different half of the valve is used for a different audio channel to see if it is an issue on one of the halves of that valve. Based on your comments/questions, I'd strongly recommend you get someone that knows what he is doing to work on it.

Yeah, those voltages can bite !

When you get the buzz, does the sound drop out, or is it overlaid, and the audio drops in volume ?

Does the buzz change in volume when the volume control is moved ?

Since i's intermittent, I would really doublw check your eacrthing in the circuit. All those earthing points as disignated with the 3 stacked dashes must be clean and solid, especially if they are connected to any metal bits. And preferably joined at a single point, or at least joined with a good chunk o wire.

Hi There!

The buzz is consistent when I can hear it, and it's not affected by volume.

Unfortunately I have been flat out at work so I haven't had a chance to check what is causing it, but it's not so much intermittent as affected by different things attached to the AMP as best I can tell.

I intend to get try my best to get to the bottom of the specifics causing the buzz so I can at least give someone a direction to head.

One thing I am sure about, is that I heard the noise at home and at work, so it's obviously not environmental.

networkn

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#1263617 19-Mar-2015 18:26

Niel: Manuals will not help, the issue is with the assembly itself. Someone would need to check it out. Where in the country are you?

Auckland NZ.

richms

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#1263660 19-Mar-2015 19:30

networkn:
Filtering is working around the problem which doesn't normally exist on this device.

No, filtering is part of good electronic design. The only evidence of that on the design is the reesitors and capacitors in the power supply. Still plenty of space for the noise to couple across from many other places, and with that large point to point construction its not hard to make a nice antenna for it as well.

The world is much more full of RF in the air and on power lines than 60 years ago when that design was state of the art.

Richard rich.ms

Niel

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#1263728 19-Mar-2015 22:30

Check if the 100uF capacitor is the right way round. If it is, the swap the 100uF from the one channel with the 100uF of the other channel to see if the noise follows. Check the contacts on the valve holders, maybe one does not make proper contact. You should be able to bend it a little bit with a thin nail or thick needle.

I'm in Pakuranga if you want to drop in, but just a bit busy for the next few weeks.

Photos of the assembly might help, including what the solder joints look like.

You can never have enough Volvos!

Aredwood

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#1263769 20-Mar-2015 01:23

richms: There are tubes with 2 sets of whatever in them. Even some with way more.

I tried an amp with that and there was crosstalk and Intermodulation between the 2 sides. Apparently that is what gives different tubes their "character".

Still should be able to swap halves of the tube around and see if it follows. There is 50hz ac sitting in them on the heater so buzz from that is quite common. Also without filtering that supply it will nicely couple other noise to a wire beside it running to the grid for amplification.

Also depending on how you have done the ground wiring. Can cause big problems. Even if the end circuit is still the same.

I'm Willing to take a look at it. I'm on the north shore if that helps.

Sorry about my earlier comments on valve circuits. Compared to an ipod or computer sound card. Your amp will be a massive improvement in sound quality. Yet there are transistor amps that are far better again. It is simply a case of knowing the limitations of your circuit.

In both my cars I have homemade voltage regulator circuits controlling their alternators. Yes they do the job. Yes I enjoyed building them. Do they regulate the voltage as precisely as the factory electronic ones - no. But they still work better than a mechanical voltage regulator ever will. So in a way I'm doing the same as you. Building a circuit that meets my needs. Even though there are better circuits available.

networkn

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#1263951 20-Mar-2015 11:43

Here are the photos of the unit, they are large as I thought it might be useful to zoom.

https://www.dropbox.com/sh/x4sj9t9a1wuaqi7/AADBTYdyCKvj6n1qpUiRy1t_a?dl=0

Let me know if you want more or different angles or closer up shots.

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Trade NZ and US shares and funds with Sharesies (affiliate link).

Aredwood

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#1263991 20-Mar-2015 12:15

Hard to tell for sure but looks like you have done the ground wiring wrong. Which means the ripple current from the bridge rectifier will be inducing voltages in other parts of the circuit. And you are probably getting earth loops as well.

SepticSceptic

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#1264006 20-Mar-2015 12:59

On pic 2, your input sockets are not grounded at the point of entry. You have connected the input ground together, fed them thru the plaited cable, and connected them to the ground at the pot ? As the signal input travels right next to the transformer and the ripple DC;, etc, it's an opportune place for hum/buzz pickup.

Earth the input at the pint of entry. And use shielded cable from the input to the pot, also grounding the shield. You already have earthed the metal judging by the output connector at the bottom left of pic 2.

networkn

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#1264026 20-Mar-2015 13:27

SepticSceptic: On pic 2, your input sockets are not grounded at the point of entry. You have connected the input ground together, fed them thru the plaited cable, and connected them to the ground at the pot ? As the signal input travels right next to the transformer and the ripple DC;, etc, it's an opportune place for hum/buzz pickup.

Earth the input at the pint of entry. And use shielded cable from the input to the pot, also grounding the shield. You already have earthed the metal judging by the output connector at the bottom left of pic 2.

Hi There!

One of the guys here had a look and suggested that if the buzz isn't affected by volume, the issue must be at the secondary stages of the AMP? The stage you are talking about is before the volume, so wouldn't volume affect it?

His opinion is that in photo4 he thinks I have damaged the capacitor and it could be from this, I thought I'd bring it to the groups attention in case that was possible?

networkn

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#1264046 20-Mar-2015 14:09

Ok well it's all very strange, for the last few days, despite being able to hear it relatively clearly at home and work, it's now almost inperceptible, I hadn't had chance to change the source much over the last few days in case it was aggravated by that, but it's very very quiet now.

Unsure if that helps with diagnosis!

Niel

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#1264216 20-Mar-2015 17:44

The cap looks fine, just slight melting of the PVC sleeve.

I think you need to fix the 0V wiring to a star connection. Use the metal plate as your 0V/common and take all 0V connections directly to it (or the nearest nut/bolt). Your 0V wire is forming a loop. This is just my gut instinct without (yet) thinking about it.

You can never have enough Volvos!

networkn

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#1264330 20-Mar-2015 22:09

Niel: The cap looks fine, just slight melting of the PVC sleeve.

I think you need to fix the 0V wiring to a star connection. Use the metal plate as your 0V/common and take all 0V connections directly to it (or the nearest nut/bolt). Your 0V wire is forming a loop. This is just my gut instinct without (yet) thinking about it.

I'm afraid that didn't mean much to me, but after it was suggested I hadn't grounded it properly I went through the instructions again and checked and the pictures of the assembly are the same as I have done it.

I think it needs someone to eyeball it properly.

SepticSceptic

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#1265668 23-Mar-2015 12:36

Grounding loops can cause all sorts of weird issues - hence follow what Niel and myself have mentioned. Proper grounding is essential - you are mixing high voltages with low level voltages, and any effects are magnified.

Star grounding means all your earth points are to a single earthuing bolt/nut.

With my previosu comment, the buzz could have been picked up by the length of back wire between the input and the pot, and radiated to the signal wires.

But since the buzz has dropped away, it very much sounds like an intermittent connection - have you used star washers for the grounding points ?

Hmm, a bit of a search, seems you purchased as a kit ? The site shows the same wiring as you have done:
http://bottleheadnginx.bottleheadcorp.netdna-cdn.com/wp-content/uploads/2014/01/crackunderside.jpg

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#1288791 21-Apr-2015 20:46

Oh Blessed Blessed Silence!

A MASSIVE thank you to Niel who kindly had a look at the unit for me and identified the issue. Despite having checked the wiring a few hundred times, it turns out for one of the Tubes, I had connected but not soldered two of the joints which as I understand it (now) was causing a ground loop issue (I think?), and because it wasn't soldered, when I was moving it, it was sometimes moving and causing minorly different results. I was under the mistaken impression that so long as metal was touching metal, it should be enough. (Though had I of spotted it, I would have soldered it.)

3 quick solders later and I finally have the amazing silent sound I wanted.

If you have any interest in electronics and headphones, I can't strongly enough recommend it. It was great fun, and I learned a little (I still don't really have a clue). It's also a VERY good Amp, esp with 600ohm headphones.

Next step after I listen to it for a few more hours, is to install the Speedball upgrade for this. Hopefully I won't need rescuing this time! :)

Once again, huge thanks to Niel, and in fact all of you, for your assistance.

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