Nashou66 Posted February 4 Posted February 4 (edited) I am also a member of AudioKarma and started a thread on my rebuild of a BA-1000. As many know the schematic and service manual are near impossible to come by. Anyone have one ? Here is my thread . I made the mistake of rebuilding before taking voltages on the harness to the Vfets while installed and also more importantly when removed so I could make sure the rebuild voltages are on par with the original with Vfets removed. This way i would be able to make sure the rebuild went well and I could reinstall them with out worry . Here are the voltages I got with Vfet's removed after the build in this link . https://live.staticflickr.com/65535/54306945470_4f749d8e4e_b.jpg Any one have a BA-1000 they would be willing to possible remove the Vfet's and take the measurements to help me verify my voltages? I know its a big ask but it help out a lot. Thanks in advance Athanasios Edited February 4 by Nashou66
Nashou66 Posted February 4 Author Posted February 4 (edited) Adjusting the Bias trimpot adjusts the voltages on the Source pins of all the V-fets ( these are removed as of now). The Gate and Drain pins are unaffected. Does this sound right or an indication I can re introduce the V-fets to the unit? I used a translator and then edited the only parts of the service manual I could find images of. I attempted to make a board layout diagram from a photo of the bottom of the PCB. some traces are hard to see. Edited February 4 by Nashou66
Nashou66 Posted February 9 Author Posted February 9 Looking at the two diagrams from the J-fet testing document floating around for testing Them and V-fets it shows a diode for each fet . So I decided to use diodes between the gate and source and in the direction shown in these diagrams shown below N-Channel And P channel So I put diodes from source to gate with the cathode facing the direction for each channel type to mimic the V-vet more closely than a simple resistor. My thought process was that the source voltage would not contaminate the Gate voltage , now was this the correct deduction? Maybe not but I think it worked. For the SK's I now get negative voltages and the SJ's I get positive. All Neg probes to chassis , positive on gates at the sockets . FT701 2SK70 = -16 v FT703 2SJ20 = +16 v FT702 2SK70 = -13.5 v FT704 2SJ20 = +14.8 As the amp was on longer the voltages got closer to each other on all four Gates . Video showing my test . Athanasios
Nashou66 Posted February 12 Author Posted February 12 I still can't find a schematic so I am attempting to make my own using the free web program on Digikey called Scheme-it . NOt sure what I'm doing but Im giving it a shot. this is how far I got so far. I can give the link to the project if anyone can cleaan that mess up for me lol Athanasios
Luc Posted February 13 Posted February 13 @pete_mac If Pete is online, then he's your man @Nashou66. Both he and his Dad are the acknowledged Sansui guru's both here and over there in your land 1 1
pete_mac Posted February 13 Posted February 13 1 hour ago, Luc said: @pete_mac If Pete is online, then he's your man @Nashou66. Both he and his Dad are the acknowledged Sansui guru's both here and over there in your land You're a good man Luc! Sadly we have no experience with these v-fet beasties!
Nashou66 Posted February 13 Author Posted February 13 5 hours ago, pete_mac said: You're a good man Luc! Sadly we have no experience with these v-fet beasties! Thanks Gentlemen . I'll continue with my schematic attempt. I messaged this blogger Yama-Chan as he has the schematic . So we'll see what happens. https://ameblo-jp.translate.goog/luxman-yamachan/entry-12519671438.html?_x_tr_sl=ja&_x_tr_tl=en&_x_tr_hl=en&_x_tr_pto=wapp Athanasios
Nashou66 Posted February 15 Author Posted February 15 Did a little more work on the Schematic . Not to nice looking but its getting there . The Scheme-it program does not allow for easy changes with out riding out entire nets of traces instead of just the trace you want to remove .
Nashou66 Posted February 16 Author Posted February 16 Latest Schematic Attempt Red 1 and 2 are outputs to the , I think, protection circuit/Relay Pin out Table Pin 1= 29 or BE : D SJ20 Pin 2= 30 or W : S SJ20 Pin3= 31 or BL : S SK70 Pin4 = 32 or GY : G SJ20 pin5 = 33 or BR : G SK70 Pin6 = 34 or OR : D SK70
Nashou66 Posted February 18 Author Posted February 18 I think this may be the drive and timing circuit completed . I may add the outputs to it as well.
Nashou66 Posted February 19 Author Posted February 19 (edited) I think I may be ready for the V-fets . I have some 2SK76's and one 2SJ26 from a Yamaha Organ that were not used in the amp section but for the power supply. So they are not worth much to me and if they fail it wont be a big loss. Saved them for this type of situation. Athanasios Edited February 19 by Nashou66
Nashou66 Posted February 27 Author Posted February 27 This mighht be the end of the line for this scchematic. Might add resitor and cap values. I would add voltages but with it not working correctly its not going to be correct I would assume. 1
Nashou66 Posted February 28 Author Posted February 28 Does any one have one of these they would be willing to take some voltages at the output traasitor sockets and also at the headers that go to them. Also maybe from the heat sunk transistors on the drive circuit. Without proper voltages the schematic is not very helpful. Also its not the best layout as I have very little schematic design experience., and the program used does not lend very well to making changes with out ripping out other traces that I don't need changed.
Nashou66 Posted March 3 Author Posted March 3 I figured it out !!! I realized after re checking the transistors I pulled what the pin outs were for each . I discovered I had TR05,06 pinouts wrong !! I failed to see that the 2SC1124's are EBC and the KSC2690's I used are ECB !!! Pulled them and put in new ones with the correct pin alignment and the unit came out of protection !! I was able to dial in the 53mV's and the correct voltages were at the gates for the Yamaha V-fets I was using as test units!!! Taking a break for now and will install the NEC V-fet's next. But I might see if these Yamaha's pass a decent sound . I remember one had a very weak curve trace , so we'll see how these two perform. Athanasios 1 1
Nashou66 Posted March 3 Author Posted March 3 (edited) 47 minutes ago, pete_mac said: Well done!! Thank you !!! Edited March 3 by Nashou66
Nashou66 Posted March 4 Author Posted March 4 All cleaned up, fresh paint for top and the sub-faceplate. looks great I think !. 1
mbz Posted March 5 Posted March 5 The digikey tool is nice freeware for circuit drawing. Better to use a free circuit simulator such as microcap or ltspice it provides the added advantage of running simulations and provides node voltages etc... Suggest microcap 12 as it has an extensive component library, the learning curve is not that great with only a few essential "hot keys" to be learnt like spacebar and rotate and... 1
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