The more I look into this problem the more I believe that this is data corruption from a bad upgrade.  No lights, no boot, no visual anything.  Yet I can read power at the PCB & at all of the IC's (16vdc, 3.6vdc, etc). 

I'm going with trying to use a basic chip programmer (ala Arduino/Serprog) and trying to 'flash' the M25P16 serial memory chip.  Problem here is I believe I need a binary file from a working amp to write to the non working unit and I don't know where to get that from (other than from another amp). 

Any suggestions?

 

I'm looking at a Blackstar ID Core 40 that will not power up.  It uses an external laptop type power supply & it's putting out 16vdc to the PCB.  I do not have a schematic for this unit and doubt I'll ever see one given Blackstar's policies.  So I'm pulling data sheers for the various IC's & checking voltages.  Eyeballing the board reveals no obvious issue.

But...I'm reading that a few other folks have experienced dead/brick problems with this line after performing firmware updates via the 'Insider' software app that Blackstar has.  It allows access to patches & a bunch of features but also checks for & installs firmware releases.  Like other firmware updates, if they do not go in perfectly they can cause a total lack of communication & indications just like no power.

Has anyone had any experience with this firmware issue?  The microcontroller on this is a LPC4330FET180...180 ball array that I am not even close to being at home with.  Should I consider this a 'brick' and sell it as wall art or is there a path to repair?  Past experience with the USA distributor and parts supplier tells me that a replacement PCB would be difficult to obtain as well as costly. 

Just looking for thoughts and direction.  This project has me in the deep end of the pool.

Hard to locate anyone selling reverse log pots.  Closest I could find in Mouser's inventory was BI Technologies / TT Electronics 20K and even they are on order & not due in until 4/16.  They list 25K Alpha's but min order is 1000 & non-stock item. 

This discussion got me thinking of trying one on a 5005 Lead 12.

And here I thought I knew something about these.  Many thanks for taking the time to post the details.  I never grasped the design relationship of these to their 50/100w cousins.  Supercharged indeed. 

Beautiful explanation.  I remain in awe...but learning.

Thank you sir.

I have a 5005 combo that has a Celestion G10N-40 in it.  I wouldn't change a thing on that amp.  Love the sound. 

But now a question regarding speaker impedance.  The 5005 combo & the 3005 head/stack versions of these amps profess to have 8 ohm output load (the micro stack being 2 ea 16 ohm/parallel).  I was always of the understanding that in the world of solid state amps one never went below the 'rated' output impedance, lest the output transistors/power amp become toast.  These amps are ok at 4 ohms?

Quote from: phatt on August 14, 2015, 08:11:25 AM

Hey Clyde,
              Just spent the last few weeks testing out many amp designs and also different size and voltage power transformers.

I'd say the difference from 40VA to 50VA is minuscule.
You would only be able to perceive this difference in an A/B test which is a lot of trouble to setup anyway.
A tiny bit more clean headroom is all that would happen.
just quietly,,,, your money might be better spent on a higher SPL speaker.

my 2 cents worth,,

Phil.

Thanks Phil,

Here's the deal on these PT's for these amps.  The 3005/5005 Lead 12's are a few years old now & I'm seeing more & more posts in various forums about owners in search of replacements for whatever reason.  So, using one of mine as a test bed, I wanted to see what would be a reasonable replacement that fit specs & retained tone.  That lead me to the Hammond choices in my initial post.  Difference simply being the 1A/28VA unit vs the 2A/50VA.  Cost difference is fairly negligible.  I questioned the Marshall spec rating of 40VA but I figure that the designer had to have a reason. 

I understand the higher SPL speaker swap.  Micro-stack or combo version, these amps generally benefit from a speaker upgrade from the Celestion G10D-25's that came as issued.  My current experiment is based solely on a maintenance/longevity quest for a substitute part that I can honestly say: "Yes, I tried it & it works".  I don't have $$ to burn but this isn't much more of a cash outlay than auditioning a set of bass strings or tubes.  Still cheaper than a boat.  So far.

Yup.  Why'd you buy a boat?  Well, I had this can of varnish...

OK...late response on the outcome here.  I picked up a can of oil based marine spar varnish, removed & dipped the power trans.  Did the trick as far as 'noise'.  Plus, I get that new-boat-smell for a bit.  Makes me feel like I really got something new too.  The down side was that the varnish cost almost as much as one of the Hammond trannys.

And just to satisfy my own curiosity, I am going to order one of the Hammond 166L28 transformers & install it just to see how it works.  I'm not looking for any magic as far as tone or anything...just testing out a replacement for the stock unit to see how it works as far as functionality & maintaining what tone is already there.  The higher VA rated unit was my choice based solely on the 40VA rating of the original circuit.  Just gotta know.

Thanks again, JMF.

Thank you, Mr. Fahey.  I'll give that a try.  Hopefully the environmental regulations in my part of the world still allow for such a product to be sold & used. :duh 

I've worked on a number of these amps over the years & own this 3005 & one of it's combo cousins, a 5005.  I love these both for sounds produced & simplicity of design (sort of).  Each one a bit unique in some quirky way and all sound wonderful to my ear.  The only things I ever seem to mess with are trying different op amps & changing the input resistor to 1M.  Everything else just seems to work as designed.  This one in the only unit that I've come across that had a trans 'issue'. 

I'll give this trans an oil varnish dip & post back with results.  Thanks again for the guidance. :dbtu: 

Thanks for the comments.  The transformer in question has not failed...just produces a lot of noise that appears to be of a mechanical nature.  Tightening things up hasn't helped but I'm still in the problem identification stage.  Trans is outputting correct voltage.  And I replaced all of the e-caps as what was there was all original & 30 years or so old.

My initial thought was just replace the trans.  Then, trying to find a suitable replacement became more of a search than I expected (i.e. no info on original).  Then it morphed into a matter of principle in finding something that would work.  Not trying to improve the sound necessarily. But then too, it is somewhat of an experiment in seeing how a different trans will affect the overall amp. 

C

Looking at replacing a transformer on a Marshall 3005.  Can't find any info on the original tranny.  Only mark on it is 'T4942'.  Per available schematics this matches & breaks down to a 115VAC with a CT 28VAC (14.3 per side...so 28.6) secondary.  Input also indicates 35w & 40VA.

The closest thing I can find as a replacement is from Hammond:  either their p# 166J28, which is a 1A, 28VA unit, or p# 166L28, which is a 2A, 50VA unit.  My 1st inclination is to go with the larger VA rating rather than undercutting.  The smaller rated unit will match for size but there's room enough for the larger. 

Am I thinking this through properly?  Any thoughts would be appreciated.

C