Again Troubles with Roland Bolt-30 - Dead/ Unknown parts

[Gokarna]

Hello to everyone there,

I have again big troubles with my Roland Bolt-30.

First only the overdrive channel didn't work and the reverb sounded dumb and (too short), now also the clean channel is dead.
The guitar signal doesn't go through the pre-amp (pcb), the power amp section works well.
I also did some mods on the amp and installed a slope resistor control poti (R63) and can here some noise from the speaker, when I turn this potentiometer.

So from my point of view, the problem must be somewhere in the first section of the preamp, around the IC-2 and/or transistor Q2 (marked red in the schematic)
I also have a problem with the notation of some of the electronical parts in the schematic (see attachment), I tried to google this, but wasn't very succesful.

So here are my question:

1. How are the "modern" notations of the following parts or what parts can I use as substitute:
- Diodes:

1S188FM
1S2473
RD-15EB
RD-30EB4
RD-47E
RD-6.8EB
RA-1SF

- Transistors:

2SK223-F or G
2SC945-GR

If somebody knows a link for the diode(s-question), I'll figure out this by myself.

The transistor 2SK223F (TO-92) is nearly impossible to find in Germany or Europe, so I would be very happy, if someone knows a common equivalent.


2. I'm still not able to understand schematics perfectly and would like to know the exact way of the guitar signal inside the red marked zone. ( 1. Clean / 2. Overdrive)

IF I'm able to repair this amp, I would like to remove the complete overdrive section (by contrast to the clean channel, it doesn't sound very good !?), but keep the channel switching in order to build my own circuit
Is anyone able and willing to mark both signal paths (Clean/Overdrive) in the schematic for me ?


3. I only have a multimeter, no oszilloscope or sound-generator. Would it make sense (and do not make more damage) to reconnect the guitar plug-in and connect it temporarly on the pcb, going backwards on the signal path starting before transistor Q3 (marked purple)?


I hope not too ask to much for a forum, I always learn the most by doing, not only be theoretical reading.
I will be very happy to get any helping answer.
Thanks to this fantastic forum (and Member "ENZO"), I already was able to fix my little Fender Sidekick-35.

I'm looking forward for your answers,

All the best and KEEP ON !!!

Till A

[Gokarna]

Hello again,
okay, this time I was more successful.

I found all the diodes beginning with RDxxx - Zener Diodes. In another forum, someone quoted, that I can use a simple 1N4148 as substitude for the 1S2473, is that true ?

The 1S188FM is sold at mcm.electronics and there are several companies selling 2SC945.
Can I use them also and solder them just reverse onto the pcb (I guess, the "R" in 2SC945-GR just means reverse !?)

Still no information to be found what kind of diode the RA1SF is
and no one to be found to sell the 2SK223 F / GR with TO-92 housing.
There are several offers of 2SK223 and 2SK2231.
Can I use these as substitude ?

Thank you for your time,

Best regards

Till A

[52 Bill]

Why do you need to replace all of those parts? Replacing them all may or may not fix your amp. You have already done a good job of isolating the problem to the red boxed area of the schematic, now you should continue and find the real problem.

If the overdrive channel stopped working and then the clean channel stopped working, look for the part of the circuit that could cause this. My first test would be the channel switching section centered around the 4016 chip IC2. Carefully read the voltages at pins 6 and 12. One pin should be high (+5) while the other one is low (0V). When you turn on the overdrive the two voltages should flip-flop, the one that was high should now be low and the one that was low should now be high. If this does not happen, you need to check the circuit around Q12. If it does flip-flop, then try changing IC2.

[gbono]

en659k_d.pdf2sk2231_en_wm_20100205.pdf

See data sheets for 2SK2231(TE16R1,NQ) & 2SK223. The 2SK2231 has lower drain to source breakdown voltage though - 60 vs 80V and different package too. Might also try 2N7002. I believe Digikey has them in stock.

You can find software on the web to turn your PC into a signal generator - search/google for a method to use an ear bud (head phone) and capacitor "probe" to "listen" to signals in your preamp transistors - be careful though since there are powerful DC levels too.

[Gokarna]

Hello again,

I don't wanted to change all the asked parts, but I'm always curious and want to know and learn....

I like to thank you;52 Bill and gbono for this very helpful first answers.
I tested the IC-2 4016 chip with my multimeter and the voltage did flip-flop betwenn pin 6 and 12. But the voltage was higher than your mentioned 5+, it was arount 11 - 12 V.
I forgot to mentioned, that I also installed the both Led's including transistors for the channel-switching as the are factory installed in the Roland Bolt-60 amp.

I also tested, if the IC-2 is grounded (pin 7) and if it has the correct voltage on pin 14 - it's a little bit lower, but I guess, that 13.94V on "D" and 6,97 on "c" will be enough.

I also measured some other point of the pcb, I'll wrote again into the schematic (orange, see schematic) and it looks okay for me.


I've smallered the red square, where I think the trouble is and from my feeling, it is somewhere around Q2.
Do you agree or would you recommend to look at IC-2 again - or anywhere else ?

Best regards,


Till A

[52 Bill]

Have you proven that IC2 is good? Having the correct voltages on the supply pins and having the switch control voltages working does not mean that the chip is ok.

[Gokarna]

Have you proven that IC2 is good? Having the correct voltages on the supply pins and having the switch control voltages working does not mean that the chip is ok.

Hi 52 Bill,

Thanks for your quick reply.

Sorry, i totally forgot to mention that.
I changes the IC-2 two times, I still have four of them here, one old one and four, that were never used before. It's very easy, because I installed long time ago a socket for each IC, so I don't have to solder them in and out.
But after you mentioned it, I also will control the connections between socket-pins and the pcb. But I'm quiet sure, that they are all very well soldered and work .


Best regards


Till A

[Gokarna]

Hello,

I did some test and work again on the amp and was successful in some points.

The transistor Q1 (Blue circle, see schematic) had a bad solder joint and Q2 (other blue circle) seems to by bad (not 100% sure of this) so I replaced it.

So the clean channel works again, but the overdrive Channel is only noticable with all potis (Volume 1, Volume 2 & Master) on 10, very quiet.
The reverb is also not working, but that's a less important subject
at the moment.

Then I realized, that there's no influence of Volume 2 on the little sound I can hear from the Overdrive channel.

I tested also all the connections of the 14-pin-socket of IC2, the are all well connected to the parts next each single pin.

Following questions:

I smallered again the red square in the first part of the schematic,but did a second red sqare around the "Volume II" -circuit, do you agree, that the problem could be also there ?

When I started this thread, I was asking about the way of the guitar signal depending on which channel is choosen.

In the attached schematic, I marked some traces green , thats what I believe is the clean-channel way, and also some purple, that's the overdrive-channel way.
Can somebody take a look on this and tell me if I'm right ?

And if yes, can I kick out the parts between the "purple lines" and connect my own developed overdrive channel there, so it will be still be switched by IC2 ?

According to this, it came to my mind, that I may check the voltage of pin 5 and 13 of IC2 - from how I understand the schematic, the two channels are both switched two times.
Is it possble, that, for example both "switches" of the clean channel work but only one of the overdrive ?


Okay, that's all for the moment, I'll take some more hours tommorrow.

Thanks for every answer,

best regards,

Till A

[52 Bill]

Now that you have fixed the clean channel sound, the distortion channel problem can be in the circuit around either Q2 or Q6, maybe both. Check the fets and the coupling caps, as well as checking for more bad solder connections, etc.

[Gokarna]

Roland Bolt-30 Troubles nearly solved - one problem (with Volume 2) left

Hi everybody

Now that you have fixed the clean channel sound, the distortion channel problem can be in the circuit around either Q2 or Q6, maybe both. Check the fets and the coupling caps, as well as checking for more bad solder connections, etc.

Thanks again, 52 Bill, for the advice to check the coupling caps.

C7 (above Q2, orange circle) in the schematic was bad.

Now also the Overdrive-channel works again, but Volume 2 (VR 6) still doesn't work as it should. Even if turned on "0", the channel works, if the other two other potis (Volume1 & Master) are not at "0".
Cranked up, the sounds loses some bass and may be also a little bit of its loudness until 7-8. Then, turned to 9 /10, it wins again a little loudness, but no bass.

I resolderes the potentiometer (VR 6); tested it, but it's okay. So I changed C18, C19, the transistor Q6 and the two diodes D7,D8.(All parts inside the red box, see schematic

But this did not help.

Any suggestions, what and where the problem might be ?

Regards, Till

P.S. I managed to repair also the reverb, very simple: IC1 was also blown.

[52 Bill]

Now also the Overdrive-channel works again, but Volume 2 (VR 6) still doesn't work as it should. Even if turned on "0", the channel works, if the other two other potis (Volume1 & Master) are not at "0".
Cranked up, the sounds loses some bass and may be also a little bit of its loudness until 7-8. Then, turned to 9 /10, it wins again a little loudness, but no bass.

I resolderes the potentiometer (VR 6); tested it, but it's okay. So I changed C18, C19, the transistor Q6 and the two diodes D7,D8.(All parts inside the red box, see schematic

According to the schematic setting VOL 2 to zero should kill the audio in the channel. That being said, there could be enough crosstalk bypassing the control to give the thin sounding signal that you describe.

If you have checked the pot and are certain that the ground connections to it are good then it may be something that you will have to live with. When you set up the distortion channel sound why would you need to set VOL 2 to zero anyway?

[Gokarna]

Works again !!!

Hello,
I solved all problems, also Volume 2 can be used as it was designed for.

Thanks to anyone, who replied here to my thread.

It's great to be here !

Best regards,

Till A

[loomis]

I just picked up a Bolt 60. Tubes are lit, but no output whatsoever.

Curious what Gokarna did exactly to evenually fix his amp?

Thanks

[52 Bill]

I just picked up a Bolt 60. Tubes are lit, but no output whatsoever.

Curious what Gokarna did exactly to evenually fix his amp?

Thanks

Hey, welcome to the place. You should start a new thread as your amp is entirely different from the solid state Bolt 30. Did you try a different speaker? Did you try plugging in a spare guitar cord into the fx loop jacks?

[loomis]

Hey, welcome to the place. You should start a new thread as your amp is entirely different from the solid state Bolt 30. Did you try a different speaker? Did you try plugging in a spare guitar cord into the fx loop jacks?

Hi and thanks for the reply. However, both the Roland Bolt 30 and the Roland Bolt 60 are tube amps with solid state preamps. I have not yet looped the effects loop, but will tomorrow. And yes, mine is a head running right into a known good speaker.

The amp has not yet been recapped, but I would assume I'd get some output even if the caps were going bad.

Loomis