stay at home type 69 project

[dogears]

300 mV RMS is around -8 dBu. If you add 20 dB you're hitting +12 dBu. At 30 you're trying to push +22 dBu which will clip.

 

[pahstah]

With a ohmmeter check that, at every click of the gain switch, the correct resistor is activated. With the Grayhill switch I once made the mistake to put the stop pins in the right position but the shaft wasn't in the start position so I activated the wrong resistor.

 

[TwentyTrees]

... With the Grayhill switch I once made the mistake to put the stop pins in the right position but the shaft wasn't in the start position so I activated the wrong resistor.

Yes, 100% this! Been there myself.

 

[Janalex]

An instruction manual comes in the tube with the gray hills. Follow it exactly. There is a specific start position around 2 o’clock

 

[fritzmyname]

The first thing I'd check is solder joints, and double-check that all your transistors are in the right spots. Its easy to put a PNP in for NPN (ask me how I know) haha. From the photos you posted everything looks ok, though.

If you have a scope, I'd start checking the signal one block at time.

first at the input between 8 and 10 on the card edge - start
at the pad switch
at pin 5 of the input transformer - before the first amplifier block
at H2 pin 1 - after the first amplifier block, before the hpf
at the connection of C10 and R25 - after the hpf
at pin 2 / common of the EQ cut switch - before the eq makeup amp
at the connection of C52 / R50 / R49 - before the output buffer
And then at the output between pins 2 and 4 on the card edge

if you don't have a scope, you can do the above with a mulimeter and a sine wave but you won't get as much out of it. try like 0.5 vrms at the input. I got a tiny handheld scope from amazon that works way better than it has any right to which is nice to have lying around.

double check also that the voltage at pin 3 of the regulator U1 is indeed +8 V over common (pin 2 of U1).

Hello thank you for the tips, I will try that. I was busy these last weeks finishing up a production for a new band so I couldn't really focus on that.

I sadly don't have a scope but a good DMM. What tiny handheld scope from amazon do you have haha?

Could you maybe state how high the voltages at either point should be? So I can compare.

Concerning the transistors I bought them according to the BOM so I doubt that there could be a mix up. What should I look out for when checking that? I mean they look the same haha.

Could this problem have something to do with the input transformer? I used the Cinemag and not the Jensen? I checked the wiring tho before sodlering it in, so the transformer itself is not damaged (had that problem once with a CAPI 2622)

Thanks!

 

[dogears]

if everything is set at unity gain, most of those points should be unity. the exception is at pin 2 of the EQ cut, that will have a loss.

 

[fritzmyname]

Thank you! Could you recommend me your scope?

 

[dogears]

honestly it was the cheapest one on amazon. theres a black friday deal for $30 today.

 

[oongbac]

Tested gain switch with DMM. I think stop pins were set correctly.

 

[Janalex]

Hey all,

I bought the 4 PCBs from fritzmyname and stuffed them a little while ago. I patiently waited for Cyril's transformers and will be receiving them this week. He told me about some changes to the input section needed to adjust the frequency response. Nothing major. However, I would really love to employ the -20db secondary option on his transformer. I looked at some Helios schematics and in fact there was a line, 0, and -20 switch. Unfortunately I dont think this is possible without drilling another small hole in the front panel for a SPDT switch since I would alternatively need a 3 way 3 pole switch to replace the PAD switch and don't think they make those in a size that would fit there. I am however not all that experienced with builds and if anyone has other options that wouldn't require extra drilling please advise.

Thanks,
Jan

 

[Janalex]

I think I have an option. subminiature 2md6 on-on-on dpdt switch to replace the HPF will offer three options. hpf on with -20 and without -20 and hpf off.

 

[Cyril Jones]

Hi Jan. Read my mail before moving on. Cyril

 

[fritzmyname]

I bought the 4 PCBs from fritzmyname and stuffed them a little while ago

Would love to see your progress!

In other news I would love to have some time to get mine working haha

 

[Janalex]

Upon first start up today I’m having the same issue described in the last posts by two others. Running a dynamic mic pad off it only responds to transients and otherwise no signal to speak of in the DAW. Haven’t even tried line level yet cause this is discouraging. The H9M board has been tested? I need to solder an extender to start taking measurements but already assuming it will be the same as others.

 

[dogears]

Hi guys. There is clearly an issue here but I don't know what it is. Twentytrees has built these boards with no problem and we make a product that is functionally identical to the circuit here. I'm sorry that there's a problem, but I've been over the pcb and schematic and can't find any difference for the life of me.

 

[oongbac]

That is not anybody's fault. Of course sometimes I feel frustrated during debug but that feeling came from my ignorance about circuitry. I think this is part of DIY. I'm enjoying this build and procedure for debug, and try my best to find out why. I'll take some risks for granted.

 

[Janalex]

I’m sure if twenty trees successfully built the h9m then we will get through this. Tomorrow I’m gonna start taking some measurements and report back

 

[fritzmyname]

It's definitely a bonding experience that we're not alone in this haha

@dogears did you change anything in the PCB file? Could there be anything that the PCB plant screwed up because we are too inexperienced when ordering PCBs?

Could there be any parts that we screwed up ordering? Can you check the BOM? Maybe @dogears can identify some critical parts that we maybe screwed up ordering? I for one used the Cinemag transformer and had to resort to slightly different C values when ordering.

As far as I remember @TwentyTrees had a nother solution for the 24V regulator circuit than we have in the current PCBs. Could there be a screwup?

I just checked the pictures on the IAA website and the design is not exactly the same for the H9. Could you identify the problem areas that would cause such issues? It seems we all deal with the same problem here so maybe we can find where there is a problem. Would it be an option if you checked the current PCB version yourself (meaning produciing one to verify that the GERBER file is not the issue)?

 

[fritzmyname]

Upon first start up today I’m having the same issue described in the last posts by two others. Running a dynamic mic pad off it only responds to transients and otherwise no signal to speak of in the DAW. Haven’t even tried line level yet cause this is discouraging. The H9M board has been tested? I need to solder an extender to start taking measurements but already assuming it will be the same as others.

Have you finished all of your 4 units?

 

[Janalex]

All my pcbs are stuffed i just only wired one of the front panels cause I wasn’t sure where to put the stop pins. I’m not so sure the second stop in is the same for the EQ and the gain. Gain is 6 positions only and for that I used 12 o o’clock and 6 o’clock and it stops correctly. For the 11 position eq switches I believe it could be what twenty trees posted. Can you confirm ?