Search found 190 matches

by jrb32
Thu Mar 14, 2019 4:28 am
Forum: Vintage Amps (Before 1991)
Topic: Mark III no distortion channel 3
Replies: 27
Views: 1282

Re: Mark III no distortion channel 3

In lead mode, volume 1 pull bright works. This does not have any effect when the amp is NOT in lead. I think you mean Lead Bright - Pull Bright on Volume 1 does actually work in both Lead and Rhythm modes, although it doesn't have much of an effect after around 8 on Volume 1. Apart from that I seco...
by jrb32
Wed Mar 13, 2019 6:20 am
Forum: Vintage Amps (Before 1991)
Topic: Buffers & the Mark II FX Loop
Replies: 2
Views: 622

Re: Buffers & the Mark II FX Loop

My first question—does this apply to IIC+ upgrades? (My amp is an '83 IIC upgraded to a + at a later stage) All C+ upgrades end up the same as all other C+s in the end from a circuit point of view and an FX loop point of view. Exactly the same. Anyone who says otherwise is misinformed. The preamp c...
by jrb32
Tue Mar 12, 2019 8:19 am
Forum: Mark Series
Topic: Converted IIC+ with Export Transformer
Replies: 6
Views: 551

Re: Converted IIC+ with Export Transformer

At the end of the day - try it out if it's local! If it blows you away then buy it for the 2000-2500 price range. If not then don't. It's simple. It's well maintained, authentic and is the most desirable out of the non EQ models apart from a coliseum.
by jrb32
Tue Mar 12, 2019 8:16 am
Forum: Mark Series
Topic: Converted IIC+ with Export Transformer
Replies: 6
Views: 551

Re: Converted IIC+ with Export Transformer

Yeah you 100% want an EQ to dial in tones. So you'd need to buy the Mesa Graphic EQ pedal separately and put that in the EQ loop separately. Looks a solid amp though and circuit wise it looks good with the correct maintenance done. It's also an RP11A which, although it was upgraded to IIC+ specs lat...
by jrb32
Fri Mar 08, 2019 5:45 am
Forum: Mark Series
Topic: Converted IIC+ with Export Transformer
Replies: 6
Views: 551

Re: Converted IIC+ with Export Transformer

https://forum.grailtone.com/viewtopic.php?f=3&t=84402&p=521552 Price wise I'd rank them as follows from worth the highest to the lowest. (K=Coliseum D=Simul, H=100W, S=60W, R=Reverb, G=Graphic) KRG DRG HRG SRG KG DG HG SG KR DR HR SR K D H S Then based on that you can add in the following for more v...
by jrb32
Fri Mar 08, 2019 5:32 am
Forum: Vintage Amps (Before 1991)
Topic: Simul,s outer
Replies: 1
Views: 195

Re: Simul,s outer

I think 470s were used until pentode operation on the Mark IIIs and IVs came in. Then they used 2.7K. Someone out there might know the difference though. I'd stick with 470 though. For context Henz's power board is missing pin 1 on the power sockets, hence the reason to replace them. Just copy other...
by jrb32
Tue Mar 05, 2019 4:52 am
Forum: Vintage Amps (Before 1991)
Topic: Cap that shouldn't be?
Replies: 5
Views: 620

Re: Cap that shouldn't be?

Stick with 470 Ohm. The more I think about it, the more I think 2.7K might be used for Pentode wiring as I haven't been able to find it used before the Green Stripe Mark III or the Mark IV but I could be wrong. 5W or similar rated 470 Ohm wirewound resistors would do the job properly and hold up bet...
by jrb32
Mon Mar 04, 2019 7:44 am
Forum: Mark Series
Topic: MK II C Mysteries
Replies: 3
Views: 974

Re: MK II C Mysteries

RP11A IIC Schematic: https://drive.google.com/open?id=1_KWgnYKephAlJAnfH8IL9El8qHdo5nji RP11A IIC Layout : https://drive.google.com/open?id=1CALqxt8hsJK_ghfb4ZnNmY8LQ627h54b The IIC schematic for the RP11 is the best I can get it without tracing one first hand. Looks like there is some weird stuff g...
by jrb32
Mon Mar 04, 2019 7:43 am
Forum: Mark Series
Topic: Mark IIC to C+ Steps Required for Upgrade
Replies: 4
Views: 790

Re: Mark IIC to C+ Steps Required for Upgrade

RP11A IIC Schematic: https://drive.google.com/open?id=1_KWgnYKephAlJAnfH8IL9El8qHdo5nji RP11A IIC Layout : https://drive.google.com/open?id=1CALqxt8hsJK_ghfb4ZnNmY8LQ627h54b RP11A IIC+ Schematic: https://drive.google.com/open?id=1SRE-Dthwda_-Wq0oRresd9D8matOy4qY RP11A IIC+ Layout: https://drive.goog...
by jrb32
Mon Mar 04, 2019 4:56 am
Forum: Vintage Amps (Before 1991)
Topic: Cap that shouldn't be?
Replies: 5
Views: 620

Re: Cap that shouldn't be?

I think it's to do with the brightness and I believe Mike B confirmed with you that the early factory Simul Classes had this 1000pF around the 270K along with a 10pF cap instead of the usual 20pF for simul. I've added it to my list of mods and notes. Cheers.
by jrb32
Fri Mar 01, 2019 11:49 am
Forum: Mark Series
Topic: Mark IIC+ - Guide for Dummies
Replies: 203
Views: 177777

Re: Mark IIC+ - Guide for Dummies

I've been analysing the history and development boards used for the IIC+ in massive detail and have a theory but it doesn't fit with the narrative exactly about winter '83. It seems like it should have been a good few months earlier maybe summer '83 when Doug West and Mike B were experimenting. Basi...
by jrb32
Fri Mar 01, 2019 7:58 am
Forum: Vintage Amps (Before 1991)
Topic: Mark III no distortion channel 3
Replies: 27
Views: 1282

Re: Mark III no distortion channel 3

You should be able to work this out without needing a video from the info I've given you. I'd recommend taking it to someone who repairs valve amps at this point. Replacing LDR2 and physically inspecting around V3 is the first place of call if that doesn't fix it. There was also a case where an LDR ...
by jrb32
Tue Feb 26, 2019 5:18 am
Forum: Mark Series
Topic: Updated Mark III+ Info
Replies: 23
Views: 7838

Re: Updated Mark III+ Info

Err where to start... .Anyway, that 15u , like the some other bypass caps, is it a 10v tantalum? Yes. Usually a T110. Could be a 20V or higher though. Or a yellow bullet T322. Or whatever they had spare at the time... I'm a little tech savvy but obviously not enough I don't want to stop you tinkerin...
by jrb32
Tue Feb 26, 2019 4:40 am
Forum: Mark Series
Topic: Mark III to Mark II mod
Replies: 74
Views: 21927

Re: Mark III to Mark II mod

Might have found a typo/error in the IIC+ schematic, it says delete C30 but that's going by the III's naming. Looks like C30 on a III is C32 on a II? Yeah just checked some pictures of a couple of DRG IIC+s and they have what I'm calling 'C32' removed and 'C30' present on the IIC+. These numbers ar...