Beiträge von R0BERT

Hello Bernd
Sorry mate, I didn't realise you were an employee.
Of course, I am eager for help.
I have learnt a lot by doing the build. You are right about measuring all resistors
before soldering - but in my rush to construct, I didn't do this.
Lesson learnt!
I'm hoping you are right. I will remove one of the resistors and check its resistance.

As you say, there is probably something else I need to identify.

I thought you suggested starting up different threads?
MUst have got that wrong.
I will restrict myself to a single thread about the A15mk2
Is it me or are there very few postings about building this amp?
Perhaps some have been archived.

Hello all
Here is another thread that documents my quest to build a hand-wired (by me) valve amp that works.
Big problem: as detailed in another post, voltage readings on power tubes triple the value they should be.
Had a couple of great suggestions from Nils and Bernd.
Haven't tried Bernd's yet, but Nils mentioned checking the value of the resistors 51 and 52 on the wiring map.
I went through them all. Those two are fine.
But...
7 resistors (R5, R23, R30, R33, R45, R46 and R64) which are supposed to be 220K / 2W, are in fact 270K / 2W. This comes down to a misreading of the colour code on the resistors (not by me!) 220K = Red, red, yellow, gold. These are Red, violet, yellow, gold (=270K). In all fairness, the violet does look quite similar to red, but it isn't, it's violet.

So, if this difference is significant - and I have to work on the assumption that it is - then I will have to replace all seven before proceeding.
The bad news is that one of these (R64) is on the underside of the power board.

I'll wait for some responses as to whether this mistake is a potential cause of my problem or if the difference is immaterial.
But I have to say: I am just a bit pissed off........

Bernd
Thanks for this.
You've provided some extremely useful advice
Robert

That's just what I was thinking.
I think they're way out.
Don't like to crit the musikding guys but the kit had bits missing and
maybe the labelling was duff.
I only started checking the resistor values on the DMM towards the end of the build.
I'll unsolder them and do a reading. They're supposed to be 1R / 2W.
Robert

Thanks Nils
I'll check this.
If I remember correctly, both readings were way out: think it measured slightly less at pin 8 of V6
something like 120 v.
I'll check again anyway though
Robert

Hello Bernd
OK, I'll check them. On the schematic it says "All voltages measured... at No-Load Conditions"
Does that mean without the tubes, or without any guitar input?

By power tubes you mean valves 4, 5 & 6 right?
Or do I pull them all out?
I'm new to this and the learning curve has been quite steep, so excuse the basic questions!

Like Vince, I'm a bit worried about my voltage readings.
On this amp there is supposed to be a reading of more or less 35Mv at pin 8 of valve 5.
I'm getting something way higher: 126.8.
Has anyone built this amp and experienced similar problems?

Fuse burn out 0.2A on A15

Hello all
Got the amp working well. Fantastic range of tones.
But then, the music died.
The smaller of the fuses burned out.http://forum.musikding.de/vb/images/smilies/eek.gif
I am now worried about where to start in terms of checking things.
I suppose it might be the variable resistor that needs adjusting.
Anyone had any experience of adjusting this or could give me some pointers
as to what I should be checking?
Thanks
Roberto

Zitat von MAD;313760

Robert,
thanks for your offer, I will contact you (I'm just planning to review and update some manuals anyway).
Regards,
Martin

Whenever you're ready
best wishes
Rob

Hello again Martin
It's working well now thank you.
One of the shielded cables was badly soldered so the signal was getting lost.
By the way, if you can send me a non pdf version of the English manual, I can improve it for you.
I am a teacher educator and English is my specialism.
My email is rob.smith@wlv.ac.uk
Regards
Robert

Yes.
Thanks for this.
What can I say? I've got the kit. I've used your instruction manual.
I've put the kit together. I'm trouble-shooting.
I'm looking to get it working.
Regards
Robert

Hello all
Just completed the wire-up. Measured voltages etc. Plugged it in, valves glowed nicely. But while there is the quietest of hisses from the speaker I've connected, the jack input is totally dead. Needless to say, no signal from my guitar is getting through. My leads are pukka - so I must have have cocked up the wiring somewhere....
Here is a link to some photos.
http://s1130.photobucket.com/albums/m535/B0BB0/
Any help or advice gratefully received.
Cheers
Robert

In fact, I think you are right, having replaced one resistor and measuring it off the board, the value changed.
I will have to check the rest of the wiring.
Will post photos and ask for suggestions.
Robert

Hello Martin
You may, of course, be right.
I am a newbie at this and am only learning how to wire up let alone read the meter correctly!
However, for a number of resistors, there is a discrepancy between the value in the inventory and the reading, e.g. R15 & R16 should be 470K but read 354; R28 should be 470K but reads 150; r47 should be 56K, reads 145K.
R 17 is down as 2M2/0 now wired in, it reads .471
While you are there, how do I do readings of the first group of resistors, those with a R value e.g. 100R/2W?
Thanks for your help and advice.
Robert

Hello Martin
Just finished wiring up A15. Valves are on but no sound and input jack socket isn't 'live'. This is my first major amp project so, learning by doing.
Have discovered that a number of the resistors I received are duff and will replace these. Photo of initial wire up available here:
Musikding people also left out all input jacks.
http://s1130.photobucket.com/upload/albums/B0BB0/
When I work out how to start my own thread, will post question to forum.