SlewMaster Builds

[yngvejos]

Thanks. 🙂

 

[yngvejos]

Is there any shorter versions of the slewbaby? The one in post 502 is 160mm long. Most of the FR4's I ordered are 150mm long. :/

 

[jwilhelm]

Terry's latfet Slewbaby was 100mm.

 

[yngvejos]

I'm planning to build with BJT's as I have a broken HK690 (fell down from a shelf in my garage and got all the pots damaged) that I want to use transistors and psu from, so I guess I can't use the latfet version?

 

[jwilhelm]

It shouldn't take much work to shorten the 2P layout to fit if you can move the fuses off the amp board.

 

[Idefixes]

Terry's latfet Slewbaby was 100mm.

Some think like this?

Marc

 

[chobot123]

Output inductor

I'm about to wind the output inductors. According to what I read here, it's made of 16 AWG enameled wire.
I almost bought a 16 SWG wire not knowing that there is difference between AWG and SWG.
I found a table http://www.cadceptual.co.uk/images/uploaded/guides/awg-swg-tables-download-original.pdf that says
16 AWG = 1.29mm diameter
while
16 SWG = 1.63mm diameter
I think it's not a big deal to use 16 SWG instead of 16 AWG, but maybe this information (new at least for me) would help some other members.

 

[jwilhelm]

The inductor value isn't critical. People use anything from 18AWG to 14AWG without changing winding methods.

 

[AndrewT]

16swg = 1.6mm diam is a good size to use for an output inductor.
Wind the turns around an AA battery sized bobbin (14.5 to 15mm diam).
8Turns gives ~ 0.7uH
12T ~ 1.5uH

Big wire gives less resistance, thus less output impedance and is more robust.

 

[Rakeman]

I used 18T with 1.2mm diam and 12mm core, is this okay?`(build not finished yet)

 

[jkuetemann]

Never been sure why the obsessive attention surrounding the coil; the finished value is not very important. Seems virtually any value from about 0.6uH to 2.4uH will be perfectly serviceable with no meaningful difference in performance. Just make a nice neat coil with the thickest wire practical that fits the board.

 

[Rakeman]

Cool, thanks. According to calculations, mine should be around 1.35uH

 

[yngvejos]

Kypton v coming up. My first time etching. 🙂

 

[still4given]

Very nice!

 

[yngvejos]

Thanks. I'm very happy with the result. I use a Brother laser printer and rumours say that they can't be used for toner transfer. I had a lot of failed attempts before I ended up using Christmas gift wrapping paper. Combined with lots of pressure and not too high temperature I finally get consistent transfers. 🙂

 

[yngvejos]

Some Slewbabys coming up. 😉

 

[Liliya]

I still have problems with one channel of my Slewmaster. The IPS works well (see post 1857). Without the bulb tester fuses blows. Today I found that Q104 was mounted the wrong way. So, I was very optimistic after mounting a "fresh" MJE340 and with emitter pointing the right way. I have measured all transistors B-E. This is what I measured(all V):
Q109 to Q118: all between 0,610(lowest) to 0,618(highest).

Q 107: 0,558 and Q108: 0,550.

Q101: 0,635. Q102:0,617. Q103:0,571. Q104: 0,447!! Q105: 0,599. Q106 0,613.

All measurement except for Q104 I think is quite normal(?) What disapointed me was 0,447 V on Q 104, witch is very close to what I measured when Q104 was mounted the wrong way(0,420V)

I have not tried the fire up without the bulb. Can I? Is any measuring results pointing to other problems for the reason that the fuses blows.

Eivind S

 

[jwilhelm]

Are you able to get bias current to zero now?

 

[Liliya]

With the bulb tester connected I measured around 25 mV on every output pair and with the biaspot turned to zero ohm.

Eivind S

 

[yngvejos]

Try turning clockwise to decrease bias. Higher resistance = lower bias.
The bulb probably limit max bias to 25mv.