Sessionette 75 fuse burn out

I bought this DOA on gumtree.ie for the price of the speaker really, knowing the fuse was blowing.


So, the fuse keeps blowing, I'm guessing I need a new power supply! What to do?
Award-Session say they stopped production of the Sessionette:75s in October 1988 and the company stopped making guitar amplifiers of any kind in 2007. No amps left, no parts left, no technicians who know their way around this piece of kit in Dublin. The original Sessionette:75 PSU was known to fail. A replacement PSU (the PM120 power module) used to be sold but is now no longer available.

The PSU in my kit has PM120 printed on it. I wonder if has my box had a replacement power module fitted before? Everything on the inside is tidily soldered and attached, it looks like a production version.

Symptom:
Turning on the power, indicator light (red) glows briefly (1s) then slowly fades. Power fuse is blown. Repeat, same. Switch power on/off quickly, same result. No obvious heat smell.
Conclude: Something is shorting.

Step 1
Inspect the circuit boards visually front and back to spot anything obvious.
Don't forget to use the nose to smell a burn.
Any discolouration on components? Nope, except perhaps a tarnish on one of the balanced power op amps (mj11015 pnp and mj11016 npn op amp). Note: can source the mj11015 and mj11016 from www.awatronic.fr at reasonable prices if needed.
(mj11015: Transistor PNP Darlington 120V 30A 200W TO-3 MOTOROLA (Equivalent: BDX68C) - Diode de protection intégrée)
(mj11016: Transistor NPN Darlington 120V 30A 200W TO-3 MOTOROLA (Equivalent: BDX69C) - Diode de protection intégrée

Conclusion? Nothing obviously wrong.

Step 2

Poke around with a multi-meter (MM) looking for shorts/continuity in unexpected places. No luck with this on either the power amp circuit or the pre amp circuits.
An observation, with everything soldered in place, I can't assess circuit behaviour without power. Why? Because (for example) discharged capacitors are shorts (for a while) until they charge up (sucking charge from the MM).
Continuity tests aren't that useful unless there's a smoking gun (burn out somewhere). Continuity is more for finding breaks (i.e. no continuity) as opposed to shorts (too much continuity).

Question? WHAT is the metal box on the inside of the cabinet connected to the pre amp by two signal cables (co-ax plugs)?
Answer? It's a three spring reverb effect from Accutronics (www.accutronicsreverb.com/). See www.amplifiedparts.com/ for an Excellent explanation of spring reverb effect box design and theory written by Kurt Prange.

Conclusion? Nothing obviously wrong.

Step 3

Hmm, isolate sections and inspect for expected/unexpected behaviour.
This is going to be difficult without a bench supply, an oscilliscope, and other stuff.

kids cartoons 001

incredible visualisation tools

Processing and processing.js
http://processingjs.org/
http://www.processing.org/

Assessing video pieces

I use the following framework for assessing presentations.

*. Does it keep to the time-limit?
*. Originality and own work; citation and acknowledgement when other material used (weighting applied to all factors).
1. Communication abilities (audio, spoken, visual, written).
2. Shown competence using advanced media tools.
3. Argument demonstrates analytical skills.
4. Message and conclusions give evidence of reflective thinking and deep engagement with an advanced research topic.
5. Overall impression: Is piece competent and polished? Has producer showcased their domain knowledge and professionalism.

Help for groups

A set of really interesting video pieces on the practicalities and challenges of student group dynamics surrounding the preparation and delivery of a group project.

Learnhighergroupwork.com (creative commons license for most of the material on this site)

Also, an incredible collection of chapters and book sections on visual literacy and visual practices.

James Elkins pages at the School of the Art Institute of Chicago

Video pieces for learning and my E-Portfolio

For me the creation of student-authored video pieces is intended to satisfy the following goals.

As a way to deliver assignments.

To showcase my own capabilities.

Act as a reflective learning aide for myself.

My goal is to show that I can engage with specialised subject matter, present it in a well organised manner. I will succeed by conveying the depth my my knowledge of a topic and by making my arguments and conclusions convincing. I may not be 100% right but I will at least have a well informed opinion.

The video piece is evidence that I have good communication abilities. It shows that I am a competent user of advanced media tools. The organisation of the argument demonstrates my analytical skills. The message and conclusions show the extent of reflective thinking I have undergone to present this advanced research topic. If I collaborate with another to produce the video then that will also indicate my ability to team work. If the finished product is competent and polished then I have showcased my professionalism.

Some benefits of self (or collaboratively) authored video reports are that they give me a high degree of freedom to present the work; I have full control over the content and presentation. Others can see my work at different places and points in time, I'm not limited to a 'once-off' slideware based presentation. Producing a video version of my research forces a kind of economy and focus that other media relax, so, in going from my report to a script, to a 'tight' script and final video my research conclusions are steadily refined and distilled to a compact 'essential message' while at the same time my more expansive written report or script is there behind the presentation to 'back it up.' My video report is an accessible and engaging element of my learning portfolio, and as it is digital I can direct people to it to demonstrate both my thinking on a particular topic and the fact that I have successfully produced material in this medium. The process of producing both expanded and compact presentations of my research in various media (text, slides, direct presentation, video & voice over) drives the process of reflective learning.

Related reading:

E Portfolios in Assessment (Holtzman & Hadley, 2009)

Action Learning Programming Concepts

I made this clip to set out a few thoughts on the learning process and describe an action based approach to orchestrating learning about computing and programming concepts. The students in this case were primary school students but the activities are equally valid for other groups.

My motivation was prompted the Google For Educators' teaching academy. While I didn't consider taking part I thought the call was interesting, relevant and challenging.