stay at home type 69 project

[Janalex]

Package came late so just had 30 minutes to replace the regulator and move the diode and measure. My voltages are now prettt much exactly as oongbac. Don’t have time to listen but presumably problem is solved.

 

[fritzmyname]

Package came late so just had 30 minutes to replace the regulator and move the diode and measure. My voltages are now prettt much exactly as oongbac. Don’t have time to listen but presumably problem is solved.

Very cool! Can you maybe show the other side of the board too and explain which connections you broke and how you connected the two Cs back?

I'm still waiting for my 7908.

 

[Janalex]

I will shoot a pic later. Just remove the diode and place it where the 7808 outside pins were. The 7908goes where the diode was. The pin closest to the connector needs to go to the grounded third contact. The middle pin slides right down into the hole and the last pin needs an extension as shown. I am still debating whether to use the caps as my datasheet for the Texas Instruments regulator doesn’t show any caps.

 

[Spacecowboy]

I will shoot a pic later. Just remove the diode and place it where the 7808 outside pins were. The 7908goes where the diode was. The pin closest to the connector needs to go to the grounded third contact. The middle pin slides right down into the hole and the last pin needs an extension as shown. I am still debating whether to use the caps as my datasheet for the Texas Instruments regulator doesn’t show any caps.

Use the caps. Might help won’t hurt. Look at the LM317 datasheet for reference.

 

[Janalex]

I installed the caps and the input one blew right upon startup. Think I’ll hold off. However good news is that i have a fully operational channel so I can just replicate this one to the other 3 over the next few days. Still need a very specific on-on-on subminiature switch to employ the -17db tap. I reached out to the manufacturer. Would like to replace the hpf switch with this dpdt switch.

 

[Spacecowboy]

You had it backwards. on the negative rail + goes to common, - to the -V.

 

[Janalex]

Both caps on the regulator plus goes to common?

 

[oongbac]

Yes.

 

[fritzmyname]

Alright, the 7908 came yesterday and today I finally had time to rip out the 7808 and rearrange the 24 V circuit. Thank you @oongbac @Janalex and @dogears for the research.

I wired it exactly as the ref 2 schematic says and it works just as expected. And holy fk does it sound good. I am completely amazed, this thing has character!

For the Gain knob I put the stop pins not at 12 and 6 but at 11 and 6. This way, I have a "0" position before 20 so I have a setting with even less Gain if I need it. For the Mid knob I didn't put in any pins so that I can use the 6 o'clock position as A-B-comparison.

I hope future builders can use the pictures below as a reference, I included the two Cs and the diodes. I saw however, that the new Gerber file includes this new layout so in the future, this build should run a lot smoother!

Thanks everybody for your efforts! @dogears do you know by now why it works with the negative side but not with the positive side?

And on another note: I really like the design of those ELMA knobs but they are too bulky I think. And also they kinda protrude from the faceplate awkwardly because the Grayhill is so long. Do you guys have any ideas on how to get the knobs closer to the faceplate? Or do you have suggestions for cool looking knobs?

Thank you!

 

[Janalex]

I used Sifam knobs with an extra plastic nut that extends to the face plate. I’ll post pics when all 4 are wired probably Tuesday. Was able to find the on-on-on subminiature switch as well so I’ll be able to get the -20 db tap working Tuesday. I agree I’m hearing a lot of character already.

 

[oongbac]

I used this knobs. I've got from domestic supplier. Not that super neat but size is good. I think I have to replace knobs for pots to smaller ones.

And I think design of front panel is really cool with the engraving. Thanks @TwentyTrees again to provide panel design. And also thanks @dogears to provide this great project and big help to solve problems. I think I should make more of this units.(Or buy IAA H9)

 

[mdcmdcmdc]

Hi folks,

After a full year of sitting on these PCBs, I think I'm finally going to dive in and start building. Two quick questions, I noticed there have been a few revisions made to the 500-series H9M version; it doesn't look like there have been any updates to the H9R (the version I'm building), but has anyone encountered any issues with the H9R as-is in the dropbox files?

Secondly, is there a readily-available PSU (prefab or project) that would be a good choice to power 4 of these in a single 2RU box?

 

[TwentyTrees]

Secondly, is there a readily-available PSU (prefab or project) that would be a good choice to power 4 of these in a single 2RU box?

On the power supply question, I would use the POS48PSU from Silent Arts - or the FP48PSU if you want an additional utility rail for LEDs, relays or whatever. I've used a bunch of Volker's PSU boards over the year and they've all been rock solid.

Keep your toroidal power transformer as far away from audio transformers and inductors as possible, of course!

 

[TwentyTrees]

View attachment 119342

I used this knobs. I've got from domestic supplier. Not that super neat but size is good. I think I have to replace knobs for pots to smaller ones.

And I think design of front panel is really cool with the engraving. Thanks @TwentyTrees again to provide panel design. And also thanks @dogears to provide this great project and big help to solve problems. I think I should make more of this units.(Or buy IAA H9)

Excellent, they're looking great! Same for @fritzmyname. I'm very glad you were able to sort out the issues (even if we don't yet understand why it worked!).

Enjoy!

 

[dogears]

Hi folks,

After a full year of sitting on these PCBs, I think I'm finally going to dive in and start building. Two quick questions, I noticed there have been a few revisions made to the 500-series H9M version; it doesn't look like there have been any updates to the H9R (the version I'm building), but has anyone encountered any issues with the H9R as-is in the dropbox files?

Secondly, is there a readily-available PSU (prefab or project) that would be a good choice to power 4 of these in a single 2RU box?

The revs were for the 500 series power. If you send it +24V it'll be fine.

One thing I'd do (three years later) on the rackmount would be to use 11 positions on the gain switch instead of six. It would be pretty easy to solder resistors on the bottom of the pcb to do so - just solder each resistor to the switch pin you want to use, and make a bus connection to ground common to the other end of all of them. Evenly distribute them according to rev log pan law in 5 dB steps, something like this:

20-56k
25-34k
30-22k
35-9k76
40-5k1
45-2k74
50-1k5
55-787R
60-460R
65-220R
70-110R

Another thing you might do for the H9R is tack in a line driver, like a THAT 1646. If you do, use the single supply schematic attached. Two channels would just use both halves of the MC33178.

 

[Janalex]

Was curious also about the decision to settle on 24v over 32v. My understanding is most of these were 32v originally. Is it just that with modern components 32v would be overkill?

 

[oongbac]

In the earlier post, there’s a report about overheating with 32V.

 

[TwentyTrees]

Yep - as originally designed, the 2128 amplifier runs on +24VDC and doesn't handle +32V. The 22113 line amp used in later Helios 0011 modules as the make-up gain amp can run off +32V, but the amps here are all 2128 so it's +24V all the way.

 

[Janalex]

Any chance the simulation can be redone with current voltages? I have to troubleshoot one of my channels with the 7908. Voltages too high on q5, 6, 7.

 

[dogears]

sure