CRT - Akira chassis option codes. - Page 1
Forum section: electronics / repair

author: asterone
author_rank: Contributor
timestamp: April 24, 2020, 06:15:52 am
content: Hi, Im having trouble understanding the diagram for service option codes in the manual for a Akira CRT.https://4.bp.blogspot.com/-YLVj56X8Gv0/WtVyikg2uSI/AAAAAAABgjg/ev9d8zPNrbg-r3aGrbaajgKdgKNP8zsjgCLcBGAs/s1600/akira%2Boption%2Bcodes.jpghttps://electronicshelponline.blogspot.com/2018/04/akira-ct-25xg9-chassis-5n11ct-25xg9a-ct.htmlI cant make heads or tails from the diagram, im assuming some formatting issues have messed up the diagram. (I also have a hard copy of the service manual and the diagram is same.)Im trying to restore sound output, which I believe was disabled by a setting here.

author: helius
author_rank: Super Contributor
timestamp: April 24, 2020, 06:30:59 am
content: It looks very simple, just a bunch of 8-bit registers that are numbered as sequential 4-bit hex digits.The display at the top,Code:1 2 3 4 5 6 7 89 A1 3 7 1 4 0 4 6* *Means that the first nybble of the first register, "Sopdata1", is 1; the second nybble is 3.The first nybble of the second register, "Sopdata2", is 7; the second nybble is 1.Et cetera.The bits in each register are described sequentially starting from the right side (LSB first).Incidentally, I wonder at the marketing wizards that called a CRT "Akira". Is it about to EXPLODE?

author: asterone
author_rank: Contributor
timestamp: April 28, 2020, 05:31:18 am
content: Hey! thanks for the reply, it cleared up some of my confusion, but a lot still to understand, perhaps I should have posted this in the beginner section.. as ive got no training in this or similar field, just a tinkerer.So if you (or another) has the time and patience and could answer a few more questions.. id be very happy!In regards to the diagram, how does it indicate what should be input to get a desired setting, for example, turn on M decoder (option 2)? Further more what entry would be input to have all decoders on?

author: helius
author_rank: Super Contributor
timestamp: April 28, 2020, 05:43:12 am
content: If I understand what it's saying, it says that the "M decoder" is a 1 bit in the least significant position of the 3rd nybble. So if the 3rd nybble is odd, M decoder is on. The 3rd nybble being 7 as in the example means all three decoder bits are on. (as 4 + 2 + 1 = 7). That's assuming that ON = 1, OFF = 0, which is not explicitly stated but would be typical. It's possible that this logic is reversed (ON = 0, OFF = 1), as the description of Gamma Correction seems to imply: "Gamma Correction ON/OFF (0/1) (For NN5198)". Overall I would not call this the best written documentation ever, but that's typical of many Japanese products. With more experience you can sometimes guess what they're trying to say.Many of the bits are described as "Reserved for internal using, must be zero", but notice how they're all the most-significant bit of their respective nybble. This means that the hexadecimal digits for each position do not take on the full range of 0-9, A-F, but are limited to 0-7. The only exception is "NTSC QSS" which when turned on would make the first nybble equal to 9 (8 for NTSC QSS + 1 for NTSC Decoder On = 9).

author: asterone
author_rank: Contributor
timestamp: May 05, 2020, 10:15:55 am
content: hey thanks again, it all makes sense now.One more enquiry if I maywhat would the ISUD0-5 be referring to?When searching I can't find any reference to ISUD## apart from this manual

author: helius
author_rank: Super Contributor
timestamp: May 06, 2020, 07:17:18 am
content: It's not a standard acronym, just some abbreviation they were too lazy to define.Is there something in the manual that talks about a "User-Defined" port? The six bits may be used to set the state of some lines to control other equipment. "ISUD" may equal "I___ S___ User Defined". Input Switch?

author: asterone
author_rank: Contributor
timestamp: May 06, 2020, 08:04:19 am
content: Only other reference in manual is this:Partially initialize:Only initialize work parameter of NN5199 and the ninth digital and the tenth digital of function set parameter(via. ISUD0, ISUD1,ISUD3,ISUD4,ISUD5),preset as interior values.